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 functional layer thickens and then is shed during menstruation in humans and some other mammals, including apes, Old World monkeys, some species of bat, and the elephant shrew. 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.
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 major progestogen in the body. Progesterone has a variety of important functions in the body. It is also a crucial metabolic intermediate in the production of other endogenous steroids, including the sex hormones and the corticosteroids, and plays an important role in brain function as a neurosteroid.
The menstrual cycle is the regular natural change that occurs in the female reproductive system that makes pregnancy possible. The cycle is required for the production of oocytes, and for the preparation of the uterus for pregnancy. The menstrual cycle occurs due to the rise and fall of estrogen. This cycle results in the thickening of the lining of the uterus, and the growth of an egg,. The egg is released from an ovary around day fourteen in the cycle; the thickened lining of the uterus provides nutrients to an embryo after implantation. If pregnancy does not occur, the lining is released in what is known as menstruation or a "period".
Progestogens, also sometimes written progestagens or gestagens, are a class of steroid hormones that bind to and activate the progesterone receptor (PR). Progesterone is the major and most important progestogen in the body. The progestogens are named for their function in maintaining pregnancy, although they are also present at other phases of the estrous and menstrual cycles.
The corpus luteum is a temporary endocrine structure in female ovaries and is 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.
The corpus albicans is the regressed form of the corpus luteum. As the corpus luteum is being broken down by macrophages, fibroblasts lay down type I collagen, forming the corpus albicans. This process is called "luteolysis". The remains of the corpus albicans may persist as a scar on the surface of the ovary.
The anovulatory cycle is a menstrual cycle characterized by varying degrees of menstrual intervals and the absence of ovulation and a luteal phase. In the absence of ovulation, there will be infertility.
In mammalian species, pseudopregnancy is a physical state whereby all the signs and symptoms of pregnancy are exhibited, with the exception of the presence of a fetus, creating a false pregnancy. The corpus luteum is responsible for the development of maternal behavior and lactation, which are mediated by the continued production of progesterone by the corpus luteum through some or all of pregnancy. In most species, the corpus luteum is degraded in the absence of a pregnancy. However, in some species, the corpus luteum may persist in the absence of pregnancy and cause "pseudopregnancy", in which the female will exhibit clinical signs of pregnancy.
17α-Hydroxyprogesterone (17α-OHP), also known as 17-OH progesterone (17-OHP), or hydroxyprogesterone (OHP), is an endogenous progestogen steroid hormone related to progesterone. It is also a chemical intermediate in the biosynthesis of many other endogenous steroids, including androgens, estrogens, glucocorticoids, and mineralocorticoids, as well as neurosteroids.
Norgestrel, sold under the brand name Ovral among others, is a progestin medication which is used in birth control pills and in menopausal hormone therapy. It is available both in combination with an estrogen and alone. It is taken by mouth.
Luteolysis is the structural and functional degradation of the corpus luteum (CL), which occurs at the end of the luteal phase of both the estrous and menstrual cycles in the absence of pregnancy.
The luteal phase is the latter phase of the menstrual cycle or the earlier phase of the estrous cycle. It begins with the formation of the corpus luteum and ends in either pregnancy or luteolysis. The main hormone associated with this stage is progesterone, which is significantly higher during the luteal phase than other phases of the cycle. Another is the endocannabinoid anandamide AEA, where the lowest plasma AEA level is observed in the luteal phase. The opposite of the luteal phase, the rest of the two weeks, is called the follicular phase.
Dydrogesterone, sold under the brand name Duphaston, Dydroboon and Femoston, is a progestin medication which is used for a variety of indications, including threatened or recurrent miscarriage during pregnancy, dysfunctional bleeding, infertility due to luteal insufficiency, dysmenorrhea, endometriosis, secondary amenorrhea, irregular cycles, premenstrual syndrome, and as a component of menopausal hormone therapy. It is taken by mouth.
Hydroxyprogesterone caproate (OHPC), sold under the brand names Proluton and Makena among others, is a progestin medication which is used to prevent preterm birth in pregnant women with a history of the condition and to treat gynecological disorders. It has also been formulated in combination with estrogens for various indications and as a form of long-lasting injectable birth control. It is not used by mouth and is instead given by injection into muscle or fat, typically once per week to once per month depending on the indication.
Prostaglandin F2α, pharmaceutically termed carboprost is a naturally occurring prostaglandin used in medicine to induce labor and as an abortifacient.
A corpus luteum cyst is a type of ovarian cyst which may rupture about the time of menstruation, and take up to three months to disappear entirely. A corpus luteum cyst rarely occurs in women over the age of 50, because eggs are no longer being released after menopause. Corpus luteum cysts may contain blood and other fluids. The physical shape of a corpus luteum cyst may appear as an enlargement of the ovary itself, rather than a distinct mass -like growth on the surface of the ovary.
Promegestone, sold under the brand name Surgestone, is a progestin medication which is used in menopausal hormone therapy and in the treatment of gynecological disorders. It is taken by mouth.
19-Norprogesterone, also known as 19-norpregn-4-ene-3,20-dione, is a steroidal progestin and close analogue of the sex hormone progesterone, lacking only the C19 methyl group of that molecule. It was first synthesized in 1944 in the form of a mixture that also included unnatural stereoisomers of progesterone, and this mixture was found to be at least equivalent to progesterone in terms of progestogenic activity. Subsequent investigations revealed that 17-isoprogesterone and 14-iso-17-isoprogesterone are devoid of progestogenic activity. 19-Norprogesterone was resynthesized in 1951 with an improved method, and was confirmed to be the component of the mixture synthesized in 1944 that was responsible for its progestogenic activity. In 1953, a paper was published showing that 19-norprogesterone possessed 4- to 8-fold the activity of progesterone in the Clauberg assay in rabbits, and at the time of this discovery, 19-norprogesterone was the most potent progestogen known.
Quingestrone, also known as progesterone 3-cyclopentyl enol ether (PCPE) and sold under the brand name Enol-Luteovis, is a progestin medication which was previously used in birth control pills in Italy but is now no longer marketed. It is taken by mouth.
Progesterone (P4) is a medication and naturally occurring steroid hormone. It is a progestogen and is used in combination with estrogens mainly in hormone therapy for menopausal symptoms and low sex hormone levels in women. It is also used in women to support pregnancy and fertility and to treat gynecological disorders. Progesterone can be taken by mouth, in through the vagina, and by injection into muscle or fat, among other routes. A progesterone vaginal ring and progesterone intrauterine device used for birth control also exist in some areas of the world.
