The menstrual cycle is a monthly process that occurs in women of reproductive age, where the lining of the uterus is shed along with blood, known as menstruation. The menstrual cycle is regulated by a complex interaction of hormones. The hormones that regulate the menstrual cycle are:
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Gonadotropin-releasing hormone (GnRH): Produced by the hypothalamus, GnRH stimulates the pituitary gland to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH) .
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Follicle-stimulating hormone (FSH): Produced by the pituitary gland, FSH stimulates the growth of several ovarian follicles, each containing one egg.
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Luteinizing hormone (LH): Produced by the pituitary gland, LH triggers the release of a mature egg from the ovary (ovulation) .
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Estrogen: Produced by the ovaries, estrogen stimulates the thickening of the lining of the uterus (endometrium) in preparation for a possible pregnancy.
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Progesterone: Produced by the ovaries, progesterone helps to maintain the thickened endometrium and prepares the uterus for implantation of a fertilized egg.
The menstrual cycle has three phases: the follicular phase, ovulatory phase, and luteal phase. During the follicular phase, FSH and LH stimulate the growth of ovarian follicles, which produce estrogen. As estrogen levels rise, the endometrium thickens in preparation for a possible pregnancy. During the ovulatory phase, LH triggers the release of a mature egg from the ovary. During the luteal phase, the empty follicle left behind after ovulation (corpus luteum) produces progesterone, which helps to maintain the thickened endometrium. If fertilization does not occur, the levels of estrogen and progesterone decrease, causing the endometrium to shed and resulting in menstruation[...
