Estrogen (also spelled oestrogen in

British English British English is the set of Variety (linguistics), varieties of the English language native to the United Kingdom, especially Great Britain. More narrowly, it can refer specifically to the English language in England, or, more broadly, to ...

; see spelling differences) is a category of sex hormone responsible for the development and regulation of the

female reproductive system The human female reproductive system is made up of the internal and external sex organs that function in the reproduction of new offspring. The reproductive system is immature at birth and develops at puberty to be able to release matured ov ...

and

secondary sex characteristic A secondary sex characteristic is a physical characteristic of an organism that is related to or derived from its sex, but not directly part of its reproductive system. In humans, these characteristics typically start to appear during pubert ...

s. There are three major

endogenous Endogeny, in biology, refers to the property of originating or developing from within an organism, tissue, or cell. For example, ''endogenous substances'', and ''endogenous processes'' are those that originate within a living system (e.g. an ...

estrogens that have estrogenic hormonal activity: estrone (E1),

estradiol Estradiol (E2), also called oestrogen, oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of female reproductive cycles such as estrous and menstrual cycles. Estradiol is responsible ...

(E2), and estriol (E3). Estradiol, an estrane, is the most potent and prevalent. Another estrogen called estetrol (E4) is produced only during pregnancy. Estrogens are synthesized in all vertebrates and some insects. Quantitatively, estrogens circulate at lower levels than

androgen An androgen (from Greek ''andr-'', the stem of the word meaning ) is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This includes ...

s in both men and women. While estrogen levels are significantly lower in males than in females, estrogens nevertheless have important physiological roles in males. Like all

steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the adrenal cortex, hence ''cortico-'') and sex steroids (typically made in the gonads or placenta). Wit ...

s, estrogens readily diffuse across the

cell membrane The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...

. Once inside the cell, they bind to and activate

estrogen receptor Estrogen receptors (ERs) are proteins found in cell (biology), cells that function as receptor (biochemistry), receptors for the hormone estrogen (17β-estradiol). There are two main classes of ERs. The first includes the intracellular estrogen ...

s (ERs) which in turn modulate the expression of many

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

s. Additionally, estrogens bind to and activate rapid-signaling membrane estrogen receptors (mERs), such as GPER (GPR30). In addition to their role as natural hormones, estrogens are used as

medication Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preventive medicine, prevent disease. Drug therapy (pharmaco ...

s, for instance in

menopausal hormone therapy Hormone replacement therapy (HRT), also known as menopausal hormone therapy or postmenopausal hormone therapy, is a form of hormone therapy used to treat symptoms associated with female menopause. Effects of menopause can include symptoms such ...

, hormonal birth control and feminizing hormone therapy for transgender women,

intersex Intersex people are those born with any of several sex characteristics, including chromosome patterns, gonads, or genitals that, according to the Office of the United Nations High Commissioner for Human Rights, "do not fit typical binar ...

people, and nonbinary people. Synthetic and natural estrogens have been found in the environment and are referred to as xenoestrogens. Estrogens are among the wide range of endocrine-disrupting compounds (EDCs) and can cause health issues and reproductive dysfunction in both wildlife and humans.

Types and examples

The four major naturally occurring estrogens in women are estrone (E1),

(E2), estriol (E3), and estetrol (E4). Estradiol (E2) is the predominant estrogen during reproductive years both in terms of absolute serum levels as well as in terms of estrogenic activity. During

menopause Menopause, also known as the climacteric, is the time when Menstruation, menstrual periods permanently stop, marking the end of the Human reproduction, reproductive stage for the female human. It typically occurs between the ages of 45 and 5 ...

, estrone is the predominant circulating estrogen and during pregnancy estriol is the predominant circulating estrogen in terms of serum levels. Given by

subcutaneous injection Subcutaneous administration is the insertion of medications beneath the skin either by injection or infusion. A subcutaneous injection is administered as a bolus (medicine), bolus into the subcutis, the layer of skin directly below the dermis and ...

in mice, estradiol is about 10-fold more potent than estrone and about 100-fold more potent than estriol. Thus, estradiol is the most important estrogen in non-pregnant females who are between the

menarche Menarche ( ; ) is the first menstrual cycle, or first menstruation, menstrual bleeding, in female humans. From both social and medical perspectives, it is often considered the central event of female puberty, as it signals the possibility of fe ...

and menopause stages of life. However, during

pregnancy Pregnancy is the time during which one or more offspring gestation, gestates inside a woman's uterus. A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Conception (biology), Conception usually occurs ...

this role shifts to estriol, and in postmenopausal women estrone becomes the primary form of estrogen in the body. Another type of estrogen called estetrol (E4) is produced only during pregnancy. All of the different forms of estrogen are synthesized from

s, specifically

testosterone Testosterone is the primary male sex hormone and androgen in Male, males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testicles and prostate, as well as promoting se ...

and androstenedione, by the

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

aromatase Aromatase (), also called estrogen synthetase or estrogen synthase, is an enzyme responsible for a key step in the biosynthesis of estrogens. It is CYP19A1, a member of the cytochrome P450 superfamily, which are monooxygenases that catalyze man ...

. Minor endogenous estrogens, the biosyntheses of which do not involve

, include 27-hydroxycholesterol,

dehydroepiandrosterone Dehydroepiandrosterone (DHEA), also known as androstenolone, is an endogenous steroid hormone precursor. It is one of the most abundant circulating steroids in humans. DHEA is produced in the adrenal glands, the gonads, and the brain. It funct ...

(DHEA), 7-oxo-DHEA, 7α-hydroxy-DHEA, 16α-hydroxy-DHEA, 7β-hydroxyepiandrosterone, androstenedione (A4), androstenediol (A5), 3α-androstanediol, and 3β-androstanediol. Some estrogen metabolites, such as the catechol estrogens 2-hydroxyestradiol, 2-hydroxyestrone, 4-hydroxyestradiol, and 4-hydroxyestrone, as well as 16α-hydroxyestrone, are also estrogens with varying degrees of activity. The biological importance of these minor estrogens is not entirely clear.

Biological function

The actions of estrogen are mediated by the

(ER), a dimeric nuclear protein that binds to DNA and controls

gene expression Gene expression is the process (including its Regulation of gene expression, regulation) by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, proteins or non-coding RNA, ...

. Like other steroid hormones, estrogen enters passively into the cell where it binds to and activates the estrogen receptor. The estrogen:ER complex binds to specific DNA sequences called a hormone response element to activate the transcription of target genes (in a study using an estrogen-dependent breast cancer cell line as model, 89 such genes were identified). Since estrogen enters all cells, its actions are dependent on the presence of the ER in the cell. The ER is expressed in specific tissues including the ovary, uterus and breast. The metabolic effects of estrogen in postmenopausal women have been linked to the genetic polymorphism of the ER. While estrogens are present in both

men A man is an adult male human. Before adulthood, a male child or adolescent is referred to as a boy. Like most other male mammals, a man's genome usually inherits an X chromosome from the mother and a Y chromosome from the fa ...

and

women A woman is an adult female human. Before adulthood, a female child or adolescent is referred to as a girl. Typically, women are of the female sex and inherit a pair of X chromosomes, one from each parent, and women with functional u ...

, they are usually present at significantly higher levels in biological women of reproductive age. They promote the development of female

secondary sexual characteristic A secondary sex characteristic is a physical characteristic of an organism that is related to or derived from its sex, but not directly part of its reproductive system. In humans, these characteristics typically start to appear during puberty ...

s, such as

breasts The breasts are two prominences located on the upper ventral region of the torso among humans and other primates. Both sexes develop breasts from the same embryology, embryological tissues. The relative size and development of the breasts is ...

, darkening and enlargement of nipples, and thickening of the

endometrium The endometrium is the inner epithelium, epithelial layer, along with its mucous membrane, of the mammalian uterus. It has a basal layer and a functional layer: the basal layer contains stem cells which regenerate the functional layer. The funct ...

and other aspects of regulating the menstrual cycle. In males, estrogen regulates certain functions of the

reproductive system The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are al ...

important to the maturation of

sperm Sperm (: sperm or sperms) is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm ...

and may be necessary for a healthy

libido In psychology, libido (; ) is psychic drive or energy, usually conceived of as sexual in nature, but sometimes conceived of as including other forms of desire. The term ''libido'' was originally developed by Sigmund Freud, the pioneering origin ...

Overview of actions

* Musculoskeletal **

Anabolic Anabolism () is the set of metabolic pathways that construct macromolecules like DNA or RNA from smaller units. These reactions require energy, known also as an endergonic process. Anabolism is the building-up aspect of metabolism, whereas catab ...

: Increases muscle mass and strength, speed of muscle regeneration, and

bone density Bone density, or bone mineral density, is the amount of bone mineral in bone tissue. The concept is of mass of mineral per volume of bone (relating to density in the physics sense), although medicine#Clinical practice, clinically it is measured by ...

, increased sensitivity to exercise, protection against muscle damage, stronger

collagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...

synthesis, increases the collagen content of

connective tissues Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesode ...

tendon A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...

s, and

ligament A ligament is a type of fibrous connective tissue in the body that connects bones to other bones. It also connects flight feathers to bones, in dinosaurs and birds. All 30,000 species of amniotes (land animals with internal bones) have liga ...

s, but also decreases stiffness of

s and

s (especially during

menstruation Menstruation (also known as a period, among other colloquial terms) is the regular discharge of blood and Mucous membrane, mucosal tissue from the endometrium, inner lining of the uterus through the vagina. The menstrual cycle is characterized ...

). Decreased stiffness of tendons gives women much lower predisposition to muscle strains but soft ligaments are much more prone to injuries ( ACL tears are 2-8x more common among women than men). ** Reduce

bone resorption Bone resorption is resorption of bone tissue, that is, the process by which osteoclasts break down the tissue in bones and release the minerals, resulting in a transfer of calcium from bone tissue to the blood. The osteoclasts are multi-nuclea ...

, increase bone formation ** In mice, estrogen has been shown to increase the proportion of the fastest-twitch (type IIX) muscle fibers by over 40%. * Metabolic ** Anti-inflammatory properties ** Accelerate

metabolism Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...

** Gynoid fat distribution: increased fat storage or estrogenic fat in some body parts such as breasts, buttocks, and legs but decreased abdominal and

visceral fat Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. It also contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, Blood vessel, vascular endothel ...

(androgenic obesity). **

Estradiol Estradiol (E2), also called oestrogen, oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of female reproductive cycles such as estrous and menstrual cycles. Estradiol is responsible ...

also regulates energy expenditure, body weight

homeostasis In biology, homeostasis (British English, British also homoeostasis; ) is the state of steady internal physics, physical and chemistry, chemical conditions maintained by organism, living systems. This is the condition of optimal functioning fo ...

, and seems to have much stronger anti-obesity effects than testosterone in general. * Other structural ** Maintenance of vessels and skin *

Protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

synthesis ** Increase hepatic production of binding proteins ** Increase production of the hepatokine adropin. *

Coagulation Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a thrombus, blood clot. It results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The process of co ...

** Increase circulating level of factors 2, 7, 9, 10,

plasminogen Plasmin is an important enzyme () present in blood that degrades many blood plasma proteins, including fibrin clots. The degradation of fibrin is termed fibrinolysis. In humans, the plasmin protein (in the zymogen form of plasminogen) is enco ...

** Decrease antithrombin III ** Increase

platelet Platelets or thrombocytes () are a part of blood whose function (along with the coagulation#Coagulation factors, coagulation factors) is to react to bleeding from blood vessel injury by clumping to form a thrombus, blood clot. Platelets have no ...

adhesiveness ** Increase vWF (estrogen ->

Angiotensin II Angiotensin is a peptide hormone that causes vasoconstriction and an increase in blood pressure. It is part of the renin–angiotensin system, which regulates blood pressure. Angiotensin also stimulates the release of aldosterone from the ...

Vasopressin Mammalian vasopressin, also called antidiuretic hormone (ADH), arginine vasopressin (AVP) or argipressin, is a hormone synthesized from the ''AVP'' gene as a peptide prohormone in neurons in the hypothalamus, and is converted to AVP. It ...

) ** Increase PAI-1 and PAI-2 also through Angiotensin II *

Lipid Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing ...

** Increase HDL,

triglyceride A triglyceride (from '' tri-'' and '' glyceride''; also TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of body fat in humans and other vertebrates ...

** Decrease LDL, fat deposition * Fluid balance ** Salt (

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

) and water retention, including facial swelling and

edema Edema (American English), also spelled oedema (British English), and also known as fluid retention, swelling, dropsy and hydropsy, is the build-up of fluid in the body's tissue (biology), tissue. Most commonly, the legs or arms are affected. S ...

** Estrogen is associated with

, including facial and abdominal swelling. *

Melanin Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. There are ...

** Estrogen is known to cause darkening of skin, especially in the face and areolae. Pale skinned women will develop browner and yellower skin during pregnancy, as a result of the increase of estrogen, known as the "mask of pregnancy". Estrogen may explain why women have darker eyes than men, and also a lower risk of skin cancer than men; a European study found that women generally have darker skin than men. * Lung function ** Promotes lung function by supporting alveoli (in rodents but probably in humans). * Sexual ** Mediate formation of female secondary sex characteristics ** Stimulate endometrial growth ** Increase uterine growth ** Increase vaginal lubrication ** Thicken the

vagina In mammals and other animals, the vagina (: vaginas or vaginae) is the elastic, muscular sex organ, reproductive organ of the female genital tract. In humans, it extends from the vulval vestibule to the cervix (neck of the uterus). The #Vag ...

l wall *

Uterus The uterus (from Latin ''uterus'', : uteri or uteruses) or womb () is the hollow organ, organ in the reproductive system of most female mammals, including humans, that accommodates the embryonic development, embryonic and prenatal development, f ...

lining ** Estrogen together with

progesterone Progesterone (; P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the ma ...

promotes and maintains the uterus lining in preparation for implantation of fertilized egg and maintenance of uterus function during gestation period, also upregulates

oxytocin Oxytocin is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary. Present in animals since early stages of evolution, in humans it plays roles in behavior that include Human bonding, ...

receptor in myometrium *

Ovulation Ovulation is an important part of the menstrual cycle in female vertebrates where the egg cells are released from the ovaries as part of the ovarian cycle. In female humans ovulation typically occurs near the midpoint in the menstrual cycle and ...

** Surge in estrogen level induces the release of

luteinizing hormone Luteinizing hormone (LH, also known as luteinising hormone, lutropin and sometimes lutrophin) is a hormone produced by gonadotropic cells in the anterior pituitary gland. The production of LH is regulated by gonadotropin-releasing hormone (G ...

, which then triggers ovulation by releasing the egg from the Graafian follicle in the

ovary The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/ oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are end ...

. * Sexual behavior ** Estrogen is required for female mammals to engage in lordosis behavior during

estrus The estrous cycle (, originally ) is a set of recurring physiological changes induced by reproductive hormones in females of mammalian subclass Theria. Estrous cycles start after sexual maturity in females and are interrupted by anestrous phas ...

(when animals are "in heat"). This behavior is required for sexual receptivity in these mammals and is regulated by the ventromedial nucleus of the

hypothalamus The hypothalamus (: hypothalami; ) is a small part of the vertebrate brain that contains a number of nucleus (neuroanatomy), nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrin ...

. ** Sex drive is dependent on

levels only in the presence of estrogen. Without estrogen, free testosterone level actually decreases sexual desire (instead of increasing sex drive), as demonstrated for those women who have

hypoactive sexual desire disorder Hypoactive sexual desire disorder (HSDD), hyposexuality, or inhibited sexual desire (ISD) is sometimes considered a sexual dysfunction, and is characterized as a lack or absence of sexual fantasies and desire for sexual activity, as judged by a ...

, and the sexual desire in these women can be restored by administration of estrogen (using oral contraceptive).

Female pubertal development

Estrogens are responsible for the development of female

s during

puberty Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a female, the testicles i ...

, including breast development, widening of the hips, and female fat distribution. Conversely,

s are responsible for pubic and body hair growth, as well as

acne Acne ( ), also known as ''acne vulgaris'', is a long-term Cutaneous condition, skin condition that occurs when Keratinocyte, dead skin cells and Sebum, oil from the skin clog hair follicles. Typical features of the condition include comedo, ...

and axillary odor.

Breast development

Estrogen, in conjunction with

growth hormone Growth hormone (GH) or somatotropin, also known as human growth hormone (hGH or HGH) in its human form, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in ...

(GH) and its secretory product

insulin-like growth factor 1 Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a hormone similar in tertiary structure, molecular structure to insulin which plays an important role in childhood growth, and has Anabolism, anabolic effects in adults. In the ...

(IGF-1), is critical in mediating breast development during

, as well as breast maturation during

in preparation of

lactation Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process naturally occurs with all sexually mature female mammals, although it may predate mammals. The process ...

and

breastfeeding Breastfeeding, also known as nursing, is the process where breast milk is fed to a child. Infants may suck the milk directly from the breast, or milk may be extracted with a Breast pump, pump and then fed to the infant. The World Health Orga ...

. Estrogen is primarily and directly responsible for inducing the ductal component of breast development, as well as for causing fat deposition and

connective tissue Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesod ...

growth. It is also indirectly involved in the lobuloalveolar component, by increasing

progesterone receptor The progesterone receptor (PR), also known as NR3C3 or nuclear receptor subfamily 3, group C, member 3, is a protein found inside cells. It is activated by the steroid hormone progesterone. In humans, PR is encoded by a single ''PGR'' gene resi ...

expression in the breasts and by inducing the secretion of

prolactin Prolactin (PRL), also known as lactotropin and mammotropin, is a protein best known for its role in enabling mammals to produce milk. It is influential in over 300 separate processes in various vertebrates, including humans. Prolactin is secr ...

. Allowed for by estrogen,

and prolactin work together to complete lobuloalveolar development during pregnancy.

Androgen An androgen (from Greek ''andr-'', the stem of the word meaning ) is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This includes ...

s such as testosterone powerfully oppose estrogen action in the breasts, such as by reducing

expression in them.

Female reproductive system

Estrogens are responsible for maturation and maintenance of the

and

uterus The uterus (from Latin ''uterus'', : uteri or uteruses) or womb () is the hollow organ, organ in the reproductive system of most female mammals, including humans, that accommodates the embryonic development, embryonic and prenatal development, f ...

, and are also involved in ovarian function, such as maturation of

ovarian follicle An ovarian follicle is a roughly spheroid cellular aggregation set found in the ovaries. It secretes hormones that influence stages of the menstrual cycle. In humans, women have approximately 200,000 to 300,000 follicles at the time of puberty, ea ...

s. In addition, estrogens play an important role in regulation of gonadotropin

secretion Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical mec ...

. For these reasons, estrogens are required for female

fertility Fertility in colloquial terms refers the ability to have offspring. In demographic contexts, fertility refers to the actual production of offspring, rather than the physical capability to reproduce, which is termed fecundity. The fertility rate ...

Neuroprotection and DNA repair

Estrogen regulated

DNA repair DNA repair is a collection of processes by which a cell (biology), cell identifies and corrects damage to the DNA molecules that encode its genome. A weakened capacity for DNA repair is a risk factor for the development of cancer. DNA is cons ...

mechanisms in the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

have neuroprotective effects. Estrogen regulates the transcription of DNA base excision repair genes as well as the translocation of the base excision repair enzymes between different subcellular compartments.

Brain and behavior

Sex drive

Estrogens are involved in

(sex drive) in both women and men.

Cognition

Verbal memory scores are frequently used as one measure of higher level

cognition Cognition is the "mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses all aspects of intellectual functions and processes such as: perception, attention, thought, ...

. These scores vary in direct proportion to estrogen levels throughout the menstrual cycle, pregnancy, and menopause. Furthermore, estrogens when administered shortly after natural or surgical menopause prevents decreases in verbal memory. In contrast, estrogens have little effect on verbal memory if first administered years after menopause. Estrogens also have positive influences on other measures of cognitive function. However the effect of estrogens on cognition is not uniformly favorable and is dependent on the timing of the dose and the type of cognitive skill being measured. The protective effects of estrogens on cognition may be mediated by estrogen's anti-inflammatory effects in the brain. Studies have also shown that the Met allele gene and level of estrogen mediates the efficiency of

prefrontal cortex In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. It is the association cortex in the frontal lobe. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, ...

dependent working memory tasks. Researchers have urged for further research to illuminate the role of estrogen and its potential for improvement on cognitive function.

Mental health

Estrogen is considered to play a significant role in women's

mental health Mental health is often mistakenly equated with the absence of mental illness. However, mental health refers to a person's overall emotional, psychological, and social well-being. It influences how individuals think, feel, and behave, and how t ...

. Sudden estrogen withdrawal, fluctuating estrogen, and periods of sustained low estrogen levels correlate with a significant lowering of mood. Clinical recovery from postpartum, perimenopause, and

postmenopause Menopause, also known as the climacteric, is the time when menstrual periods permanently stop, marking the end of the reproductive stage for the female human. It typically occurs between the ages of 45 and 55, although the exact timing can ...

depression has been shown to be effective after levels of estrogen were stabilized and/or restored. Menstrual exacerbation (including menstrual psychosis) is typically triggered by low estrogen levels, and is often mistaken for premenstrual dysphoric disorder. Compulsions in male lab mice, such as those in obsessive-compulsive disorder (OCD), may be caused by low estrogen levels. When estrogen levels were raised through the increased activity of the enzyme

in male lab mice, OCD rituals were dramatically decreased. Hypothalamic protein levels in the gene COMT are enhanced by increasing estrogen levels which are believed to return mice that displayed OCD rituals to normal activity. Aromatase deficiency is ultimately suspected which is involved in the synthesis of estrogen in humans and has therapeutic implications in humans having obsessive-compulsive disorder. Local application of estrogen in the rat hippocampus has been shown to inhibit the re-uptake of

serotonin Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...

. Contrarily, local application of estrogen has been shown to block the ability of fluvoxamine to slow serotonin clearance, suggesting that the same pathways which are involved in SSRI efficacy may also be affected by components of local estrogen signaling pathways.

Parenthood

Studies have also found that fathers had lower levels of cortisol and testosterone but higher levels of estrogen (estradiol) than did non-fathers.

Binge eating

Estrogen may play a role in suppressing

binge eating Binge eating is a pattern of disordered eating which consists of episodes of uncontrollable eating. It is a common symptom of eating disorders such as binge eating disorder and bulimia nervosa. During such binges, a person rapidly consumes an exc ...

. Hormone replacement therapy using estrogen may be a possible treatment for binge eating behaviors in females. Estrogen replacement has been shown to suppress binge eating behaviors in female mice. The mechanism by which estrogen replacement inhibits binge-like eating involves the replacement of

(5-HT) neurons. Women exhibiting binge eating behaviors are found to have increased brain uptake of neuron 5-HT, and therefore less of the neurotransmitter serotonin in the cerebrospinal fluid. Estrogen works to activate 5-HT neurons, leading to suppression of binge like eating behaviors. It is also suggested that there is an interaction between hormone levels and eating at different points in the female

menstrual cycle The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that makes pregnancy possible. The ovarian cycle controls the production and release of eg ...

. Research has predicted increased emotional eating during hormonal flux, which is characterized by high

and

levels that occur during the mid-

luteal phase The menstrual cycle is on average 28 days in length. It begins with Menstruation, menses (day 1–7) during the follicular phase (day 1–14), followed by ovulation (day 14) and ending with the luteal phase (day 14–28). While historically, medi ...

. It is hypothesized that these changes occur due to brain changes across the menstrual cycle that are likely a genomic effect of hormones. These effects produce menstrual cycle changes, which result in hormone release leading to behavioral changes, notably binge and emotional eating. These occur especially prominently among women who are genetically vulnerable to binge eating phenotypes. Binge eating is associated with decreased estradiol and increased progesterone. Klump et al. Progesterone may moderate the effects of low estradiol (such as during dysregulated eating behavior), but that this may only be true in women who have had clinically diagnosed binge episodes (BEs). Dysregulated eating is more strongly associated with such ovarian hormones in women with BEs than in women without BEs. The implantation of 17β-estradiol pellets in ovariectomized mice significantly reduced binge eating behaviors and injections of GLP-1 in ovariectomized mice decreased binge-eating behaviors. The associations between binge eating, menstrual-cycle phase and ovarian hormones correlated.

Masculinization in rodents

In rodents, estrogens (which are locally aromatized from androgens in the brain) play an important role in psychosexual differentiation, for example, by masculinizing territorial behavior; the same is not true in humans. In humans, the masculinizing effects of prenatal androgens on behavior (and other tissues, with the possible exception of effects on bone) appear to act exclusively through the androgen receptor. Consequently, the utility of rodent models for studying human psychosexual differentiation has been questioned.

Skeletal system

Estrogens are responsible for both the pubertal growth spurt, which causes an acceleration in linear growth, and epiphyseal closure, which limits

height Height is measure of vertical distance, either vertical extent (how "tall" something or someone is) or vertical position (how "high" a point is). For an example of vertical extent, "This basketball player is 7 foot 1 inches in height." For an e ...

and limb length, in both females and males. In addition, estrogens are responsible for bone maturation and maintenance of bone mineral density throughout life. Due to hypoestrogenism, the risk of

osteoporosis Osteoporosis is a systemic skeletal disorder characterized by low bone mass, micro-architectural deterioration of bone tissue leading to more porous bone, and consequent increase in Bone fracture, fracture risk. It is the most common reason f ...

increases during

Cardiovascular system

Women are less impacted by heart disease due to vasculo-protective action of estrogen which helps in preventing atherosclerosis. It also helps in maintaining the delicate balance between fighting infections and protecting arteries from damage thus lowering the risk of cardiovascular disease. During

, high levels of estrogens increase

coagulation Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a thrombus, blood clot. It results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The process of co ...

and the risk of

venous thromboembolism Venous thrombosis is the blockage of a vein caused by a thrombus (blood clot). A common form of venous thrombosis is deep vein thrombosis (DVT), when a blood clot forms in the deep veins. If a thrombus breaks off ( embolizes) and flows to the lun ...

. Estrogen has been shown to upregulate the

peptide hormone Peptide hormones are hormones composed of peptide molecules. These hormones influence the endocrine system of animals, including humans. Most hormones are classified as either amino-acid-based hormones (amines, peptides, or proteins) or steroid h ...

adropin.

Immune system

The effect of estrogen on the

immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...

is in general described as Th2 favoring, rather than suppressive, as is the case of the effect of male sex hormone – testosterone. Indeed, women respond better to

vaccine A vaccine is a biological Dosage form, preparation that provides active acquired immunity to a particular infectious disease, infectious or cancer, malignant disease. The safety and effectiveness of vaccines has been widely studied and verifi ...

infection An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...

s and are generally less likely to develop

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

, the tradeoff of this is that they are more likely to develop an

autoimmune disease An autoimmune disease is a condition that results from an anomalous response of the adaptive immune system, wherein it mistakenly targets and attacks healthy, functioning parts of the body as if they were foreign organisms. It is estimated tha ...

. The Th2 shift manifests itself in a decrease of cellular immunity and increase in humoral immunity (

antibody An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as pathogenic bacteria, bacteria and viruses, includin ...

production) shifts it from cellular to humoral by downregulating cell-mediated immunity and enhancing Th2 immune response by stimulating IL-4 production and Th2 differentiation. Type 1 and type 17 immune responses are downregulated, likely to be at least partially due to IL-4, which inhibits Th1. Effect of estrogen on different immune cells' cell types is in line with its Th2 bias. Activity of basophils, eosinophils, M2

macrophage Macrophages (; abbreviated MPhi, φ, MΦ or MP) are a type of white blood cell of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris and foreign substances, which do not have proteins that ...

s and is enhanced, whereas activity of NK cells is downregulated. Conventional

dendritic cell A dendritic cell (DC) is an antigen-presenting cell (also known as an ''accessory cell'') of the mammalian immune system. A DC's main function is to process antigen material and present it on the cell surface to the T cells of the immune system ...

s are biased towards Th2 under the influence of estrogen, whereas plasmacytoid dendritic cells, key players in antiviral defence, have increased IFN-g secretion. Estrogen also influences

B cell B cells, also known as B lymphocytes, are a type of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system. B cells produce antibody molecules which may be either secreted or inserted into the plasm ...

s by increasing their survival, proliferation, differentiation and function, which corresponds with higher antibody and B cell count generally detected in women. On a molecular level estrogen induces the above-mentioned effects on cell via acting on intracellular receptors termed ER α and ER β, which upon ligation form either homo or heterodimers. The genetic and nongenetic targets of the receptors differ between homo and heterodimers. Ligation of these receptors allows them to translocate to the nucleus and act as

transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding t ...

s either by binding estrogen response elements (ERE) on

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

or binding DNA together with other transcriptional factors e.g. Nf-kB or AP-1, both of which result in

RNA polymerase In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that catalyzes the chemical reactions that synthesize RNA from a DNA template. Using the e ...

recruitment and further chromatin remodelation. A non-transcriptional response to oestrogen stimulation was also documented (termed membrane-initiated steroid signalling, MISS). This pathway stimulates the ERK and PI3K/AKT pathways, which are known to increase cellular proliferation and affect chromatin remodelation.

Associated conditions

Researchers have implicated estrogens in various estrogen-dependent conditions, such as ER-positive

breast cancer Breast cancer is a cancer that develops from breast tissue. Signs of breast cancer may include a Breast lump, lump in the breast, a change in breast shape, dimpling of the skin, Milk-rejection sign, milk rejection, fluid coming from the nipp ...

, as well as a number of

genetic condition A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosome abnormality. Although polygenic disorders are ...

s involving estrogen signaling or metabolism, such as estrogen insensitivity syndrome, aromatase deficiency, and aromatase excess syndrome. High estrogen can amplify stress-hormone responses in stressful situations.

Biochemistry

Biosynthesis

Estrogens, in females, are produced primarily by the

ovaries The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are endocr ...

, and during pregnancy, the

placenta The placenta (: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas, and waste exchange between ...

Follicle-stimulating hormone Follicle-stimulating hormone (FSH) is a gonadotropin, a glycoprotein polypeptide hormone. FSH is synthesized and secreted by the gonadotropic cells of the anterior pituitary gland and regulates the development, growth, puberty, pubertal maturat ...

(FSH) stimulates the ovarian production of estrogens by the granulosa cells of the

s and corpora lutea. Some estrogens are also produced in smaller amounts by other tissues such as the

liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

pancreas The pancreas (plural pancreases, or pancreata) is an Organ (anatomy), organ of the Digestion, digestive system and endocrine system of vertebrates. In humans, it is located in the abdominal cavity, abdomen behind the stomach and functions as a ...

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...

adrenal gland The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer adrenal corte ...

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

adipose tissue Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. It also contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, Blood vessel, vascular endothel ...

, and the

breast The breasts are two prominences located on the upper ventral region of the torso among humans and other primates. Both sexes develop breasts from the same embryology, embryological tissues. The relative size and development of the breasts is ...

s. These secondary sources of estrogens are especially important in postmenopausal women. The pathway of estrogen biosynthesis in extragonadal tissues is different. These tissues are not able to synthesize C19 steroids, and therefore depend on C19 supplies from other tissues and the level of aromatase. In females, synthesis of estrogens starts in theca interna cells in the ovary, by the synthesis of androstenedione from

cholesterol Cholesterol is the principal sterol of all higher animals, distributed in body Tissue (biology), tissues, especially the brain and spinal cord, and in Animal fat, animal fats and oils. Cholesterol is biosynthesis, biosynthesized by all anima ...

. Androstenedione is a substance of weak androgenic activity which serves predominantly as a precursor for more potent androgens such as testosterone as well as estrogen. This compound crosses the basal membrane into the surrounding granulosa cells, where it is converted either immediately into estrone, or into testosterone and then estradiol in an additional step. The conversion of androstenedione to testosterone is catalyzed by 17β-hydroxysteroid dehydrogenase (17β-HSD), whereas the conversion of androstenedione and testosterone into estrone and estradiol, respectively is catalyzed by aromatase, enzymes which are both expressed in granulosa cells. In contrast, granulosa cells lack 17α-hydroxylase and 17,20-lyase, whereas theca cells express these enzymes and 17β-HSD but lack aromatase. Hence, both granulosa and theca cells are essential for the production of estrogen in the ovaries. Estrogen levels vary through the

, with levels highest near the end of the follicular phase just before

ovulation Ovulation is an important part of the menstrual cycle in female vertebrates where the egg cells are released from the ovaries as part of the ovarian cycle. In female humans ovulation typically occurs near the midpoint in the menstrual cycle and ...

. Note that in males, estrogen is also produced by the Sertoli cells when FSH binds to their FSH receptors.

Distribution

Estrogens are plasma protein bound to

albumin Albumin is a family of globular proteins, the most common of which are the serum albumins. All of the proteins of the albumin family are water- soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Alb ...

and/or sex hormone-binding globulin in the circulation.

Metabolism

Estrogens are metabolized via hydroxylation by

cytochrome P450 Cytochromes P450 (P450s or CYPs) are a Protein superfamily, superfamily of enzymes containing heme as a cofactor (biochemistry), cofactor that mostly, but not exclusively, function as monooxygenases. However, they are not omnipresent; for examp ...

s such as CYP1A1 and

CYP3A4 Cytochrome P450 3A4 (abbreviated CYP3A4) () is an important enzyme in the body, mainly found in the liver and in the intestine, which in humans is encoded by ''CYP3A4'' gene. It organic redox reaction, oxidizes small foreign organic molecules ( ...

and via

conjugation Conjugation or conjugate may refer to: Linguistics *Grammatical conjugation, the modification of a verb from its basic form *Emotive conjugation or Russell's conjugation, the use of loaded language Mathematics *Complex conjugation, the change o ...

by estrogen sulfotransferases ( sulfation) and UDP-glucuronyltransferases (

glucuronidation Glucuronidation is often involved in drug metabolism of substances such as drugs, pollutants, bilirubin, androgens, estrogens, mineralocorticoids, glucocorticoids, fatty acid derivatives, retinoids, and bile acids. These linkages involve gly ...

). In addition, estradiol is dehydrogenated by 17β-hydroxysteroid dehydrogenase into the much less potent estrogen estrone. These reactions occur primarily in the

, but also in other tissues.

Excretion

Estrogens are inactivated primarily by the

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

s and

and excreted via the

gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the Digestion, digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascula ...

in the form of conjugates, found in

feces Feces (also known as faeces American and British English spelling differences#ae and oe, or fæces; : faex) are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the ...

bile Bile (from Latin ''bilis''), also known as gall, is a yellow-green/misty green fluid produced by the liver of most vertebrates that aids the digestion of lipids in the small intestine. In humans, bile is primarily composed of water, is pro ...

, and

urine Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...

Medical use

Estrogens are used as

s, mainly in

hormonal contraception Hormonal contraception refers to birth control methods that act on the endocrine system. Almost all methods are composed of steroid hormones, although in India one selective estrogen receptor modulator is marketed as a contraceptive. The original ...

hormone replacement therapy Hormone replacement therapy (HRT), also known as menopausal hormone therapy or postmenopausal hormone therapy, is a form of hormone therapy used to treat symptoms associated with female menopause. Effects of menopause can include symptoms such ...

, and to treat gender dysphoria in transgender women and other transfeminine individuals as part of feminizing hormone therapy.

Chemistry

The estrogen

steroid A steroid is an organic compound with four fused compound, fused rings (designated A, B, C, and D) arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes t ...

hormones are estrane steroids.

History

In 1929,

Adolf Butenandt Adolf Friedrich Johann Butenandt (; 24 March 1903 – 18 January 1995) was a German biochemist. He was awarded the Nobel Prize in Chemistry in 1939 for his "work on sex hormones." He initially rejected the award in accordance with government pol ...

and Edward Adelbert Doisy independently isolated and purified estrone, the first estrogen to be discovered. Then, estriol and estradiol were discovered in 1930 and 1933, respectively. Shortly following their discovery, estrogens, both natural and synthetic, were introduced for medical use. Examples include estriol glucuronide ( Emmenin, Progynon), estradiol benzoate, conjugated estrogens ( Premarin),

diethylstilbestrol Diethylstilbestrol (DES), also known as stilbestrol or stilboestrol, is a nonsteroidal estrogen medication, which is presently rarely used. In the past, it was widely used for a variety of indications, including pregnancy support for those with ...

, and ethinylestradiol. The word estrogen derives from

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

. It is derived from "oestros" (a periodic state of sexual activity in female mammals), and genos (generating). It was first published in the early 1920s and referenced as "oestrin". With the years, American English adapted the spelling of estrogen to fit with its phonetic pronunciation.

Society and culture

Etymology

The name ''estrogen'' is derived from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

(), literally meaning "verve" or "inspiration" but figuratively sexual passion or desire, and the suffix '' -gen'', meaning "producer of".

Environment

A range of synthetic and natural substances that possess estrogenic activity have been identified in the environment and are referred to xenoestrogens. * Synthetic substances such as

bisphenol A Bisphenol A (BPA) is a chemical compound primarily used in the manufacturing of various plastics. It is a colourless solid which is Solubility, soluble in most common organic solvents, but has very poor solubility in water. BPA is produced on a ...

as well as metalloestrogens (e.g.,

cadmium Cadmium is a chemical element; it has chemical symbol, symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Like z ...

). * Plant products with estrogenic activity are called

phytoestrogen A phytoestrogen is a plant-derived xenoestrogen (a type of estrogen produced by organisms other than humans) not generated within the endocrine system, but consumed by eating plants or manufactured foods. Also called a "dietary estrogen", it ...

s (e.g., coumestrol,

daidzein Daidzein (7-hydroxy-3-(4-hydroxyphenyl)-4H-chromen-4-one) is a naturally occurring compound found exclusively in soybeans and other legumes, and structurally belongs to a class of compounds known as isoflavones. Daidzein and other isoflavones a ...

, genistein, miroestrol). * Those produced by fungi are known as mycoestrogens (e.g., zearalenone). Estrogens are among the wide range of endocrine-disrupting compounds (EDCs) because they have high estrogenic potency. When an EDC makes its way into the environment, it may cause male reproductive dysfunction to wildlife and humans. The estrogen excreted from farm animals makes its way into fresh water systems. During the germination period of reproduction the fish are exposed to low levels of estrogen which may cause reproductive dysfunction to male fish.

Cosmetics

Some hair shampoos on the market include estrogens and placental extracts; others contain

s. In 1998, there were case reports of four prepubescent African-American girls developing breasts after exposure to these shampoos. In 1993, the FDA determined that not all

over-the-counter Over-the-counter (OTC) drugs are medicines sold directly to a consumer without a requirement for a prescription from a healthcare professional, as opposed to prescription drugs, which may be supplied only to consumers possessing a valid pres ...

topically applied hormone-containing drug products for human use are

generally recognized as safe and effective Generally recognized as safe and effective (abbreviated as GRASE, GRAS/E, or GRAS/GRAE) is designation for certain old drugs that do not require prior approval from the U.S. Food and Drug Administration in order to enter the United States marketpl ...

and are misbranded. An accompanying proposed rule deals with cosmetics, concluding that any use of natural estrogens in a cosmetic product makes the product an unapproved new drug and that any cosmetic using the term "hormone" in the text of its labeling or in its ingredient statement makes an implied drug claim, subjecting such a product to regulatory action. In addition to being considered misbranded drugs, products claiming to contain placental extract may also be deemed to be misbranded cosmetics if the extract has been prepared from placentas from which the hormones and other biologically active substances have been removed and the extracted substance consists principally of protein. The FDA recommends that this substance be identified by a name other than "placental extract" and describing its composition more accurately because consumers associate the name "placental extract" with a therapeutic use of some biological activity.

References

External links

* Nussey and Whitehead:
Endocrinology, an integrated approach
', Taylor and Francis 2001. Free online textbook. {{Authority control Hydroxyarenes Cyclopentanols Antigonadotropins Estranes Fertility Hepatotoxins Hormones of the hypothalamus-pituitary-gonad axis Hormones of the hypothalamic-pituitary-prolactin axis Hormones of the ovary Hormones of the pregnant female Hormones of the testis Human female endocrine system Human hormones Mammal female reproductive system Prolactin releasers Sex hormones 1929 in science 1929 in Germany Sterols Puberty