Luteolysis (also known as luteal regression) is the structural and functional degradation of the

corpus luteum The corpus luteum (Latin for "yellow body"; : corpora lutea) is a temporary endocrine structure in female ovaries involved in the production of relatively high levels of progesterone, and moderate levels of estradiol, and inhibin A. It is the ...

, which occurs at the end of the

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 ...

of both the

estrous 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 phases ...

and

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 ...

s in the absence of

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 ...

Prostaglandin F2 alpha (PGF2α)

Prostaglandin F2 alpha (PGF2α) has been identified as the key luteolytic hormone in many species. PGF2α is released from uterine endometrial cells in a pulsatile pattern when stimulated by oxytocin to stimulate both luteolytic activity and further release of oxytocin from the corpus luteum.

Domestic animals

In domestic animals, luteolysis is initiated by the hormones

prostaglandin F2alpha Prostaglandin F2α (PGF2α in prostanoid nomenclature), pharmaceutically termed dinoprost, is a naturally occurring prostaglandin used in medicine to induce labor and as an abortifacient. Prostaglandins are lipids throughout the entire body tha ...

and

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, ...

and is dependent on the presence of the uterus. In sheep, communication between the pars nervosa (posterior lobe of the pituitary gland), corpus luteum, and the uterus

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 ...

via the circulatory system is required for luteolysis. Studies with sheep have found that, if the uterine horn is ipsilateral to the ovary possessing the CL is surgically removed, the lifespan of the corpus luteum will increase drastically.

Humans/Primates

Removal of the uterus in primates (including humans) does not prolong the life of the corpus luteum, indicating that a different stimulatory mechanism and source of PGF2α is responsible for luteolysis in these species. It has been proposed that PGF2α is made locally within the ovary and the corpus luteum may be the source of luteolytic PGF2α. Asthmatics should take great care when handling this hormone as PGF2α is bronchoconstrictor. During a pregnancy, the corpus luteum remains on the ovary releasing

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 ...

which will maintain a state of uterine quiescence and close the

cervix The cervix (: cervices) or cervix uteri is a dynamic fibromuscular sexual organ of the female reproductive system that connects the vagina with the uterine cavity. The human female cervix has been documented anatomically since at least the time ...

until the delivery of the fetus. Alternatively if no implantation of a

blastocyst The blastocyst is a structure formed in the early embryonic development of mammals. It possesses an inner cell mass (ICM) also known as the ''embryoblast'' which subsequently forms the embryo, and an outer layer of trophoblast cells called the ...

occurs, the corpus luteum is degraded to a

corpus albicans The corpus albicans (Latin for "whitening body"; also known as atretic corpus luteum, corpus candicans, or simply as albicans) is the regressed form of the corpus luteum. As the corpus luteum is being broken down by macrophages, fibroblasts lay d ...

(scar tissue) by PGF2α released by uterine endometrial cells. Degradation of the corpus luteum will result in reduced levels of progesterone, promoting an increase in

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) secretion by the adenohypophysis, which will trigger the development of a new follicle on 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 ...

. In humans, the placental hormone

human chorionic gonadotropin Human chorionic gonadotropin (hCG) is a hormone for the maternal recognition of pregnancy produced by trophoblast cells that are surrounding a growing embryo (syncytiotrophoblast initially), which eventually forms the placenta after implantat ...

continues to maintain the corpus luteum. This is the hormone tested for by the pregnancy test.

Equine

If pregnancy occurs in

equine Equinae is a subfamily of the family Equidae, known from the Hemingfordian stage of the Early Miocene (16 million years ago) onwards. They originated in North America, before dispersing to every continent except Australia and Antarctica. They are ...

, the placental hormone

equine chorionic gonadotropin Equinae is a subfamily of the family Equidae, known from the Hemingfordian stage of the Early Miocene (16 million years ago) onwards. They originated in North America, before dispersing to every continent except Australia and Antarctica. They ...

released by endometrial cup acts like LH and FSH and stimulates additional ovulations, although the oocytes released during these ovulations are not fertilized. The resulting accessory corpora lutea produce progesterone and keep levels of progesterone high during pregnancy.

Luteolytic agents

Danazol Danazol, sold as Danocrine and other brand names, is a medication used in the treatment of endometriosis, fibrocystic breast disease, hereditary angioedema and other conditions. It is taken oral administration, by mouth. The use of danazol is ...

was described as a luteolytic agent.Wentz AC, Sapp KC. Danazol as a luteolytic agent. Fertil Steril. 1978;29(1):23-5. *

Cloprostenol Cloprostenol is a synthetic analogue of prostaglandin F2α (PGF2α). It is a potent luteolytic agent; this means that, within hours of administration, it causes the corpus luteum to stop production of progesterone, and to reduce in size over se ...

is another example of such an agent.

References

{{Reflist * Bagnell, C. 2005. "Animal Reproduction". Rutgers University Department of Animal Sciences. * Hadley, M.E. and Levine, J.E. 2007. Endocrinology, 6th Edition. * Philip L. Sanger Menstrual cycle Human female endocrine system Theriogenology