Leydig cells, also known as interstitial cells of the testes and interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the

testicle A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testostero ...

and produce

testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of male reproductive tissues such as testes and prostate, as well as promoting secondary sexual characteris ...

in the presence 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 (Gn ...

(LH). They are polyhedral in shape and have a large, prominent

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom * Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucl ...

, an eosinophilic

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...

, and numerous lipid-filled vesicles.

Structure

The mammalian Leydig cell is a polyhedral epithelioid cell with a single eccentrically located ovoid nucleus. The nucleus contains one to three prominent nucleoli and large amounts of dark-staining peripheral

heterochromatin Heterochromatin is a tightly packed form of DNA or '' condensed DNA'', which comes in multiple varieties. These varieties lie on a continue between the two extremes of constitutive heterochromatin and facultative heterochromatin. Both play a rol ...

. The acidophilic cytoplasm usually contains numerous membrane-bound lipid droplets and large amounts of

smooth endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...

(SER). Besides the abundance of SER with scattered patches of rough endoplasmic reticulum, several mitochondria are also prominent within the

. Reinke crystals have lipofuscin pigment and rod-shaped crystal-like structures 3 to 20 micrometres in diameter. Adult-type Leydig cells differentiate in the post-natal testis and are dormant until

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 girl, the testes in a b ...

. They are preceded in the testis by a population of fetal-type Leydig cells from the 8th to the 20th week of

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during preg ...

, which produce enough testosterone for masculinisation of a male fetus.

Androgen production

Leydig cells release a class of

hormones A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required fo ...

called androgens (19-carbon

steroid A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and ...

s). They secrete

androstenedione Androstenedione, or 4-androstenedione (abbreviated as A4 or Δ4-dione), also known as androst-4-ene-3,17-dione, is an endogenous weak androgen steroid hormone and intermediate in the biosynthesis of estrone and of testosterone from dehy ...

and dehydroepiandrosterone (DHEA), when stimulated by the

(LH), which is released from the

anterior pituitary A major organ of the endocrine system, the anterior pituitary (also called the adenohypophysis or pars anterior) is the glandular, anterior lobe that together with the posterior lobe ( posterior pituitary, or the neurohypophysis) makes up the ...

in response to

gonadotropin releasing hormone Gonadotropin-releasing hormone (GnRH) is a releasing hormone responsible for the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. GnRH is a tropic peptide hormone synthesized and released ...

which in turn is released by the

hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus ...

. LH binds to its receptor ( LHCGR) which is a

G-protein coupled receptor G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily-related p ...

and consequently increases the production of cAMP. cAMP, in turn through

protein kinase A In cell biology, protein kinase A (PKA) is a family of enzymes whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA is also known as cAMP-dependent protein kinase (). PKA has several functions in the cell, including regulatio ...

activation, stimulates cholesterol translocation from intracellular sources (primarily the

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

and intracellular stores) to the mitochondria, firstly to the outer mitochondrial membrane and then cholesterol needs to be translocated to the inner mitochondrial membrane by

steroidogenic acute regulatory protein The steroidogenic acute regulatory protein, commonly referred to as StAR (STARD1), is a transport protein that regulates cholesterol transfer within the mitochondria, which is the rate-limiting step in the production of steroid hormones. It is p ...

, which is the rate-limiting step in steroid biosynthesis. This is followed by pregnenolone formation from the translocated cholesterol via the cholesterol side-chain cleavage enzyme, which is found in the inner mitochondrial membrane, eventually leading to testosterone synthesis and secretion by Leydig cells. In rats,

prolactin Prolactin (PRL), also known as lactotropin, 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 secreted from the pit ...

(PRL) increases the response of Leydig cells to LH by increasing the number of LH receptors expressed on Leydig cells.

Clinical significance

Leydig cells may grow uncontrollably and form a Leydig cell tumour. These may be hormonally active, i.e. secrete testosterone. The function of Reinke crystals is unknown, but they appear in the case of Leydig cell tumours. They are found in less than half of all Leydig cell tumors, but they serve to clinch the diagnosis of a Leydig cell tumor. No other interstitial cell within the testes has a nucleus or cytoplasm with these characteristics, making identification relatively easy. While any age is susceptible to a Leydig cell tumour, Leydig cell tumours are more common in people aged 5 to 10 and 30 to 35. A Leydig cell tumour in a child usually causes

precocious puberty In medicine, precocious puberty is puberty occurring at an unusually early age. In most cases, the process is normal in every aspect except the unusually early age and simply represents a variation of normal development. In a minority of childre ...

. About 10% of boys with the tumour have

gynecomastia Gynecomastia (also spelled gynaecomastia) is the abnormal non-cancerous enlargement of one or both breasts in males due to the growth of breast tissue as a result of a hormone imbalance between estrogens and androgens. Updated by Brent Wisse ...

. Although a Leydig cell tumour is always

benign Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...

in children, it is

malignant Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...

in 10% to 15% of adults. It is the most common

testicular cancer Testicular cancer is cancer that develops in the testicles, a part of the male reproductive system. Symptoms may include a lump in the testicle, or swelling or pain in the scrotum. Treatment may result in infertility. Risk factors include an ...

of non-

germ cell Germ or germs may refer to: Science * Germ (microorganism), an informal word for a pathogen * Germ cell, cell that gives rise to the gametes of an organism that reproduces sexually * Germ layer, a primary layer of cells that forms during embry ...

origin. Sonography may be used to identify cystic areas, but it is unable to tell benign tumours apart from malignant tumours. Adrenomyeloneuropathy is another example of a disease affecting the Leydig cell. In this case, a person's testosterone may fall despite higher-than-normal levels of LH and

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, pubertal maturation, ...

(FSH).

Etymology

Leydig cells are named after the German anatomist

Franz Leydig Franz von Leydig, also Franz Leydig (; 21 May 1821 – 13 April 1908), was a German zoologist and comparative anatomist."Franz von Leydig" (biography), Ole Daniel Enerson, 2006, WhoNamedIt.coWNI-675-Leydig Life Franz Leydig was born on 21 May 1 ...

, who discovered them in 1850.

Additional images

File:Gray1114.png, Section of a genital cord of the testis of a human embryo 3.5 cm long File:Leydig cell tumour2.jpg, Intermediate magnification

micrograph A micrograph or photomicrograph is a photograph or digital image taken through a microscope or similar device to show a magnify, magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken ...

of a Leydig cell tumour,

H&E stain Hematoxylin and eosin stain ( or haematoxylin and eosin stain or hematoxylin-eosin stain; often abbreviated as H&E stain or HE stain) is one of the principal tissue stains used in histology. It is the most widely used stain in medical diagnos ...

File:Leydig cell tumour3.jpg, High magnification

of a Leydig cell tumour,

File:Leydig cells.JPG, Cross-section of seminiferous tubules; arrows indicate location of Leydig cells

References

External links

*
Reproductive PhysiologyDiagram at umassmed.edu
{{DEFAULTSORT:Leydig Cell Steroid hormone secreting cells Animal reproductive system Human cells Scrotum