3- Laboratory Challenges of Female Infertility Diagnosis - Part III (Menstrual Cycle)

3- Laboratory Challenges of Female Infertility Diagnosis - Part III (Menstrual Cycle)

What happens in a menstrual cycle?

 Summary of menstrual cycles:

Each menstrual cycle in the ovary consists of three phases (follicular, ovulatory, and luteal). This cycle in the uterus also includes three phases of menstrual bleeding, the proliferative phase and the secretory phase. The secretory phase in the uterus is equivalent to the luteal phase in the ovary.



• The menstrual cycle begins on the first day of bleeding.



• If estrogen does not occur at the end of the previous menstrual cycle, estrogen and progesterone decrease (due to the breakdown of the corpus luteum and the formation of the corpus luteum) and the thick layer of the uterus. Falls and causes menstrual bleeding or menstruation.



• Increased secretion of LH ‌ and FSH from adenohypophysis (which occurs following a decrease in estrogen and progesterone secretion at the end of the previous menstrual cycle and the removal of the inhibitory effect of FSH secretion by estradiol). An increase in FSH peak is seen on the third day of menstruation. .



• These cells are surrounded by a layer of extraterrestrial matrix called the fibro-muscular covering, in the outer part of which Teka cells are located in two layers of internal and external Teka.



• The estrogen produced by granulosa cells circulates in the cervix and stimulates the production of mucus (this mucus facilitates the movement of sperm in the fallopian tube). .



• The estrogen circulating in the uterine wall promotes tissue growth (proliferative phase) and provides the environment for fertilization of eggs and sperm. .



• At the end of the follicular phase, a sudden increase in estrogen causes a new layer to form in the endometrium, which is histologically different from the proliferative tissue. Estrogen also increases the production of cervical mucus by creating cryptic tissues in the cervix, which prepares the environment for sperm storage and transmission.



• This positive estrogen feedback causes a sharp increase in LH (LH Surge). In general, estrogens have a low inhibitory effect on gonadotropins at low concentrations and have a stimulating effect on gonadotropin secretion at high concentrations, most likely due to the effect of various receptors. .



• Secondary oocyte, which was stopped in stage II metaphase, after release and in case of fertilization with sperm, goes through the next stages of its meiosis quickly, first to ootid - then to oum - Ovum - turns from. .



• Ovum has a maximum fertilization time of 24 hours, and disappears if not fertilized.



• If the diameter of the follicles is more than 2 cm, it is called an ovarian cyst

.

After ovulation, the follicle remains deformed and turns into a corpus luteum, which consists of a cluster of steroidogenic cells that produce large amounts of progesterone and small amounts of estrogen.



• Increased progesterone by stimulating estrogen production in the adrenal glands increases estrogen. .



• These hormones, in turn, inhibit the secretion of FSH and LH from the adenohypophysis, and only their levels remain adequate to continue the activity of the corpus luteum.



When the egg is released, the level of FSH decreases, but if the egg is not released, the level of this hormone remains high (probably trying to stimulate the ovaries to release this egg).



LH. Stimulates the secretion of progesterone from the luteal follicle (or corpus luteum or corpus luteum) and continues to secrete progesterone until the next menstrual period. .



• In the second half of the cycle, the egg enters the fallopian tube after ovulation and release in the oviduct site, at which point progesterone rises and prepares the uterus for pregnancy. If the egg is fertilized by sperm at this stage, pregnancy will occur. Otherwise, the egg disappears after 24 hours in the fallopian tube (disintegrate). .



• At the beginning of the follicular phase, FSH stimulates the granulosa cells of small antral follicles, stimulating the secretion of Inhibin B and increasing its level. As Inhibin B increases, FSH begins to decline, and as the egg is released, the amount of FSH hormone decreases further.



• Continued secretion of Inhibin A from the corpus luteum, along with a decrease in estrogen (which occurs after ovulation), has a greater inhibitory effect on FSH secretion, thereby reducing FSH levels in the luteal phase. Finds.



• Decreased levels of these two hormones after ovulation can cause very mild bleeding (spotting) in the middle of the cycle.

• Progesterone thickens the inner lining of the uterus (endometrium) and also increases blood flow and reduces the contractile strength of the smooth muscles of the uterus (secretory phase), so that it is ready to accept and feed the fertilized egg. .



• If pregnancy does not occur, estrogen and progesterone decrease (due to the breakdown of the corpus luteum and the formation of the corpus luteum) and the thick layer of the uterus falls off, causing menstrual bleeding or menstruation, which is the beginning of the next cycle.

• If pregnancy occurs, the hormone remains secreted and fertilizes the egg and sperm.

The Cytotrophoblast Sin cell, which is located in the outer layer of the blastomere and later forms the outer layer of the placenta, is responsible for stimulating the secretion of progesterone hormones from the corpus luteum by producing the hormone HCG ‌ (which has a similar structure to LH). Be.

 If pregnancy does not occur, progesterone suddenly drops and the uterine wall collapses and bleeding occurs.

 

Therefore, the levels of AMH and Inhibin B, which are produced by the granulosa cells of the growing antral and small antral follicles (containing eggs), are an indicator of the number and quality of eggs produced in the menstrual cycle. Be.