Luteolysis

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Luteolysis [1] (also known as luteal regression) is the structural and functional degradation of the corpus luteum, which occurs at the end of the luteal phase of both the estrous and menstrual cycles in the absence of pregnancy.

Contents

Prostaglandin F2 alpha (PGF2α)

Prostaglandin F2 alpha (PGF2α) has been identified as the key luteolytic hormone in many species. [2] PGF2α is released from uterine endometrial cells in a pulsatile pattern when stimulated by oxytocin [3] to stimulate both luteolytic activity and further release of oxytocin from the corpus luteum. [4]

Domestic animals

In domestic animals, luteolysis is initiated by the hormones prostaglandin F2alpha and 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 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.[ citation needed ]

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. [5] It has been proposed that PGF2α is made locally within the ovary and the corpus luteum may be the source of luteolytic PGF2α. [6] Asthmatics should take great care when handling this hormone as PGF2α is bronchoconstrictor.[ citation needed ]

During a pregnancy, the corpus luteum remains on the ovary releasing progesterone which will maintain a state of uterine quiescence and close the cervix until the delivery of the fetus. Alternatively if no implantation of a blastocyst occurs, the corpus luteum is degraded to a corpus albicans (scar tissue) by PGF2α released by uterine endometrial cells.[ citation needed ]

Degradation of the corpus luteum will result in reduced levels of progesterone, promoting an increase in follicle-stimulating hormone (FSH) secretion by the adenohypophysis, which will trigger the development of a new follicle on the ovary.[ citation needed ]

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 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

Related Research Articles

<span class="mw-page-title-main">Endometrium</span> Inner mucous membrane of the mammalian uterus

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 layer thickens and then is shed during menstruation in humans and some other mammals, including apes, Old World monkeys, some species of bat, the elephant shrew and the Cairo spiny mouse. In most other mammals, the endometrium is reabsorbed in the estrous cycle. During pregnancy, the glands and blood vessels in the endometrium further increase in size and number. Vascular spaces fuse and become interconnected, forming the placenta, which supplies oxygen and nutrition to the embryo and fetus. The speculated presence of an endometrial microbiota has been argued against.

<span class="mw-page-title-main">Menstrual cycle</span> Natural changes in the human female reproductive system

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 eggs and the cyclic release of estrogen and progesterone. The uterine cycle governs the preparation and maintenance of the lining of the uterus (womb) to receive an embryo. These cycles are concurrent and coordinated, normally last between 21 and 35 days, with a median length of 28 days, and continue for about 30–45 years.

<span class="mw-page-title-main">Ovulation</span> Release of egg cells from the ovaries

Ovulation is the release of eggs from the ovaries. In women, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells. After ovulation, during the luteal phase, the egg will be available to be fertilized by sperm. In addition, the uterine lining (endometrium) is thickened to be able to receive a fertilized egg. If no conception occurs, the uterine lining as well as the egg will be shed during menstruation.

<span class="mw-page-title-main">Luteinizing hormone</span> Gonadotropin secreted by the adenohypophysis

Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. The production of LH is regulated by gonadotropin-releasing hormone (GnRH) from the hypothalamus. In females, an acute rise of LH known as an LH surge, triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell–stimulating hormone (ICSH), it stimulates Leydig cell production of testosterone. It acts synergistically with follicle-stimulating hormone (FSH).

<span class="mw-page-title-main">Corpus luteum</span> Temporary endocrine structure in ovaries

The corpus luteum 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 remains of the ovarian follicle that has released a mature ovum during a previous ovulation.

Gonadotropins are glycoprotein hormones secreted by gonadotropic cells of the anterior pituitary of vertebrates. This family includes the mammalian hormones follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the placental/chorionic gonadotropins, human chorionic gonadotropin (hCG) and equine chorionic gonadotropin (eCG), as well as at least two forms of fish gonadotropins. These hormones are central to the complex endocrine system that regulates normal growth, sexual development, and reproductive function. LH and FSH are secreted by the anterior pituitary gland, while hCG and eCG are secreted by the placenta in pregnant humans and mares, respectively. The gonadotropins act on the gonads, controlling gamete and sex hormone production.

Abnormal uterine bleeding (AUB), also known as (AVB) or as atypical vaginal bleeding, is vaginal bleeding from the uterus that is abnormally frequent, lasts excessively long, is heavier than normal, or is irregular. The term dysfunctional uterine bleeding was used when no underlying cause was present. Vaginal bleeding during pregnancy is excluded. Iron deficiency anemia may occur and quality of life may be negatively affected.

An anovulatory cycle is a menstrual cycle characterised by the absence of ovulation and a luteal phase. It may also vary in duration from a regular menstrual cycle.

The estrous cycle 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, otherwise known as "rest" phases, or by pregnancies. Typically, estrous cycles repeat until death. These cycles are widely variable in duration and frequency depending on the species. Some animals may display bloody vaginal discharge, often mistaken for menstruation. Many mammals used in commercial agriculture, such as cattle and sheep, may have their estrous cycles artificially controlled with hormonal medications for optimum productivity. The male equivalent, seen primarily in ruminants, is called rut.

<span class="mw-page-title-main">Folliculogenesis</span> Process of maturation of primordial follicles

In biology, folliculogenesis is the maturation of the ovarian follicle, a densely packed shell of somatic cells that contains an immature oocyte. Folliculogenesis describes the progression of a number of small primordial follicles into large preovulatory follicles that occurs in part during the menstrual cycle.

Urofollitropin is a purified form of follicle-stimulating hormone (FSH) that is manufactured by extraction from human urine and then purified to remove various proteins and other substances. FSH is important in the development of follicles (eggs) produced by the ovaries. Given by subcutaneous injection, it is used in combination with human chorionic gonadotropin (hCG) to assist in ovulation and fertility. It is also used with in vitro fertilization methods. The dosage is adjusted to each individual's response.

<span class="mw-page-title-main">Luteal phase</span> The latter part of the menstrual cycle associated with ovulation and an increase in progesterone

The menstrual cycle is on average 28 days in length. It begins with menses during the follicular phase, followed by ovulation and ending with the luteal phase. Unlike the follicular phase which can vary in length among individuals, the luteal phase is typically fixed at approximately 14 days and is characterized by changes to hormone levels, such as an increase in progesterone and estrogen levels, decrease in gonadotropins such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH), changes to the endometrial lining to promote implantation of the fertilized egg, and development of the corpus luteum. In the absence of fertilization by sperm, the corpus luteum atrophies leading to a decrease in progesterone and estrogen, an increase in FSH and LH, and shedding of the endometrial lining (menses) to begin the menstrual cycle again.

<span class="mw-page-title-main">Implantation (embryology)</span> First stage of pregnancy

Implantation, also known as nidation, is the stage in the embryonic development of mammals in which the blastocyst hatches, attaches, adheres, and invades into the wall of the female's uterus. Implantation is the first stage of gestation, and, when successful, the female is considered to be pregnant. An implanted embryo is detected by the presence of increased levels of human chorionic gonadotropin (hCG) in a pregnancy test. The implanted embryo will receive oxygen and nutrients in order to grow.

<span class="mw-page-title-main">Uterine gland</span>

Uterine glands or endometrial glands are tubular glands, lined by a simple columnar epithelium, found in the functional layer of the endometrium that lines the uterus. Their appearance varies during the menstrual cycle. During the proliferative phase, uterine glands appear long due to estrogen secretion by the ovaries. During the secretory phase, the uterine glands become very coiled with wide lumens and produce a glycogen-rich secretion known as histotroph or uterine milk. This change corresponds with an increase in blood flow to spiral arteries due to increased progesterone secretion from the corpus luteum. During the pre-menstrual phase, progesterone secretion decreases as the corpus luteum degenerates, which results in decreased blood flow to the spiral arteries. The functional layer of the uterus containing the glands becomes necrotic, and eventually sloughs off during the menstrual phase of the cycle.

<span class="mw-page-title-main">Prostaglandin F2alpha</span> Chemical compound

Prostaglandin F2α, 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 have a hormone-like function. In pregnancy, PGF2 is medically used to sustain contracture and provoke myometrial ischemia to accelerate labor and prevent significant blood loss in labor. Additionally, PGF2 has been linked to being naturally involved in the process of labor. It has been seen that there are higher levels of PGF2 in maternal fluid during labor when compared to at term. This signifies that there is likely a biological use and significance to the production and secretion of PGF2 in labor. Prostaglandin is also used to treat uterine infections in domestic animals.

<span class="mw-page-title-main">Fertility testing</span>

Fertility testing is the process by which fertility is assessed, both generally and also to find the "fertile window" in the menstrual cycle. General health affects fertility, and STI testing is an important related field.

Hormonal regulation occurs at every stage of development. A milieu of hormones simultaneously affects development of the fetus during embryogenesis and the mother, including human chorionic gonadotropin (hCG) and progesterone (P4).

<span class="mw-page-title-main">Chorionic gonadotropin beta</span> Protein-coding gene in the species Homo sapiens

Choriogonadotropin subunit beta (CG-beta) also known as chorionic gonadotrophin chain beta is a protein that in humans is encoded by the CGB gene.

<span class="mw-page-title-main">Maternal recognition of pregnancy</span> Crucial aspect of carrying a pregnancy to full term

Maternal recognition of pregnancy is a crucial aspect of carrying a pregnancy to full term. Without maternal recognition to maintain pregnancy, the initial messengers which stop luteolysis and promote foetal implantation, growth and uterine development finish with nothing to replace them and the pregnancy is lost.

<span class="mw-page-title-main">Neohormone</span>

Neohormones are a group of recently evolved hormones primarily associated to the success of mammalian development. These hormones are specific to mammals and are not found in other vertebrates—this is because neohormones are evolved to enhance specific mammalian functions. In males, neohormones play important roles in regulating testicular descent and preparing the sperm for internal fertilisation. In females, neohormones are essential for regulating early pregnancy, mammary gland development lactation, and viviparity. Neohormones superimpose their actions on the hypothalamic-pituitary-gonadal axis and are not associated with other core bodily functions.

References

  1. ↑ "Luteolysis - Google Search". www.google.com. Retrieved 2020-12-18.
  2. ↑ McCracken, John A.; Custer, Edward E.; Lamsa, Justin C. (1999-04-01). "Luteolysis: A Neuroendocrine-Mediated Event". Physiological Reviews. 79 (2): 263–323. doi:10.1152/physrev.1999.79.2.263. ISSN   0031-9333. PMID   10221982.
  3. ↑ Samuelsson, B.; Goldyne, M.; Granström, E.; Hamberg, M.; Hammarström, S.; Malmsten, C. (1978-06-01). "Prostaglandins and Thromboxanes". Annual Review of Biochemistry. 47 (1): 997–1029. doi:10.1146/annurev.bi.47.070178.005025. ISSN   0066-4154. PMID   209733.
  4. ↑ Hooper, S. B.; Watkins, W. B.; Thorburn, G. D. (1986-12-01). "Oxytocin, Oxytocin-Associated Neurophysin, and Prostaglandin F2α Concentrations in the Utero-Ovarian Vein of Pregnant and Nonpregnant Sheep". Endocrinology. 119 (6): 2590–2597. doi:10.1210/endo-119-6-2590. ISSN   0013-7227. PMID   3465529.
  5. ↑ McCracken, John A.; Custer, Edward E.; Lamsa, Justin C. (1999-04-01). "Luteolysis: A Neuroendocrine-Mediated Event". Physiological Reviews. 79 (2): 263–323. doi:10.1152/physrev.1999.79.2.263. ISSN   0031-9333. PMID   10221982.
  6. ↑ Auletta, Frederick J.; Flint, Anthony P. F. (February 1988). "Mechanisms Controlling Corpus Luteum Function in Sheep, Cows, Nonhuman Primates, and Women Especially in Relation to the Time of Luteolysis". Endocrine Reviews. 9 (1): 88–105. doi:10.1210/edrv-9-1-88. ISSN   0163-769X. PMID   3286237.
  7. ↑ Wentz AC, Sapp KC. Danazol as a luteolytic agent. Fertil Steril. 1978;29(1):23-5. PMID   620838
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