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

corpus luteum The corpus luteum (Latin for "yellow body"; plural 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 t ...

, which occurs at the end of the luteal phase of both the

estrous The estrous cycle (, originally ) is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females. Estrous cycles start after sexual maturity in females and are interrupted by anestrous p ...

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 make pregnancy possible. The ovarian cycle controls the production and release of eggs a ...

s in the absence of pregnancy.

Prostaglandin F2 alpha (PGF2α)

Prostaglandin F2 alpha Prostaglandin F2α (PGF2α in prostanoid nomenclature), pharmaceutically termed carboprost is a naturally occurring prostaglandin used in medicine to induce labor and as an abortifacient. Prostaglandins are lipids throughout the entire body that ...

(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 carboprost is a naturally occurring prostaglandin used in medicine to induction (birth), induce labor and as an abortifacient. Prostaglandins are lipids throughout th ...

and

oxytocin Oxytocin (Oxt or OT) is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary. It plays a role in social bonding, reproduction, childbirth, and the period after childbirth. Oxytocin ...

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 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 functional laye ...

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. Therefore, PGF2α uterine role in regulating luteal regression has been confined to mammalian species and a different mechanism appears to control luteolysis in primates. 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 m ...

which will maintain a state of uterine quiescence and close the

cervix The cervix or cervix uteri (Latin, 'neck of the uterus') is the lower part of the uterus (womb) in the human female reproductive system. The cervix is usually 2 to 3 cm long (~1 inch) and roughly cylindrical in shape, which changes during ...

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 t ...

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, pubertal maturation, an ...

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

ovary The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. ...

. In humans, the placental hormone human chorionic gonadotropin continues to maintain the corpus luteum. This is the hormone tested for by the pregnancy test.

Equine

If pregnancy occurs in equine, the placental hormone

equine chorionic gonadotropin Equine chorionic gonadotropin (acronym given as eCG but not to be confused with ECG) is a gonadotropin, gonadotropic hormone produced in the chorion of pregnant mares. Previously referred to as pregnant mare's Blood serum, serum gonadotropin (PMSG), ...

released by

endometrial cup Endometrial cups form during pregnancy in mares and are the source of equine chorionic gonadotropin (eCG) and a placenta-associated structure, which is derived from the fetus. Their purpose is to increase the immunological tolerance of the mare in ...

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 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 s ...

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