How dose Progesterone converts the endometrium to its secretory stage to prepare the uterus for implantation
Progesterone has key effects via non-genomic signalling on human sperm as they migrate through the female tract before fertilization occurs, though the receptor(s) as yet remain unidentified. Detailed characterisation of the events occurring in sperm in response to progesterone has elucidated certain events including intracellular calcium transients and maintained changes, slow calcium oscillations, now thought to possibly regulate motility. It is produced by the ovaries. Progesterone has also been shown to demonstrate effects on octopus spermatozoa.
Progesterone is sometimes called the "hormone of pregnancy" and it has many roles relating to the development of the fetus:
- Progesterone converts the endometrium to its secretory stage to prepare the uterus for implantation. At the same time progesterone affects the vaginal epithelium and cervical mucus, making it thick and impenetrable to sperm. Progesterone is anti-mitogenic in endometrial epithelial cells, and as such, mitigates the tropic effects of estrogen. If pregnancy does not occur, progesterone levels will decrease, leading, in the human, to menstruation. Normal menstrual bleeding is progesterone-withdrawal bleeding. If ovulation does not occur and the corpus luteum does not develop, levels of progesterone may be low, leading to anovulatory dysfunctional uterine bleeding.
- During implantation and gestation, progesterone appears to decrease the maternal immune response to allow for the acceptance of the pregnancy.
- Progesterone decreases contractility of the uterine smooth muscle. This effect contributes to prevention of preterm labor.
- A drop in progesterone levels is possibly one step that facilitates the onset of labor.
- In addition progesterone inhibits lactation during pregnancy. The fall in progesterone levels following delivery is one of the triggers for milk production.
The fetus metabolizes placental progesterone in the production of adrenal steroids
Reproductive Immunology: Open Access
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