From the Research
The menstrual cycle is a complex process involving the coordinated action of the hypothalamus, pituitary gland, ovaries, and uterus, with key hormones including Follicle-Stimulating Hormone (FSH), Luteinizing Hormone (LH), estrogen, and progesterone, as described in the most recent study 1. The menstrual cycle typically lasts 28 days but can range from 21-35 days.
- The cycle begins with the hypothalamus releasing gonadotropin-releasing hormone (GnRH), which stimulates the pituitary gland to produce FSH and LH.
- During the follicular phase (days 1-14), FSH stimulates ovarian follicles to develop, with one becoming dominant and producing increasing amounts of estrogen.
- This estrogen causes the endometrium (uterine lining) to thicken.
- Around day 14, a surge in LH triggers ovulation, releasing the egg from the follicle.
- The empty follicle transforms into the corpus luteum during the luteal phase (days 15-28), producing progesterone and some estrogen.
- Progesterone maintains the thickened endometrium in preparation for implantation.
- If fertilization doesn't occur, the corpus luteum degenerates, hormone levels drop, and the endometrium sheds as menstrual bleeding, beginning a new cycle. The specific tissues, cells, and hormones involved in the menstrual cycle include:
- The hypothalamus, which releases GnRH
- The pituitary gland, which releases FSH and LH
- The ovaries, which contain follicles that produce estrogen and progesterone
- The uterus, which contains the endometrium that thickens and sheds in response to hormonal changes
- The ovarian follicle, which is composed of three key cells: theca cells, granulosa cells, and the oocyte, as described in 2. This complex interplay between the hypothalamus, pituitary gland, ovaries, and uterus ensures reproductive function and influences many aspects of female health, with the most recent study 1 providing the most up-to-date understanding of the cyclic processes involved.