From the Research
The menstrual cycle typically occurs over 28 days and consists of four main phases: menstrual, follicular, ovulation, and luteal phases. The menstrual phase (days 1-5) begins with the shedding of the uterine lining, causing bleeding that lasts about 3-7 days. Next is the follicular phase (days 1-13), which overlaps with menstruation, where follicle-stimulating hormone (FSH) stimulates follicle development in the ovaries and estrogen levels rise, causing the uterine lining to thicken, as described in 1. Ovulation (day 14) occurs when luteinizing hormone (LH) surges, triggering the release of a mature egg from the ovary. Finally, the luteal phase (days 15-28) follows, where the ruptured follicle forms the corpus luteum, which produces progesterone to maintain the uterine lining for potential pregnancy, as explained in 2. If fertilization doesn't occur, the corpus luteum degenerates, hormone levels drop, and the cycle begins again with menstruation. Some key points to consider when evaluating the menstrual cycle include:
- The role of FSH and LH in folliculogenesis, as discussed in 1 and 3
- The importance of estrogen and progesterone in maintaining the uterine lining, as described in 2 and 4
- The variation in cycle length among women, with 21-35 days considered normal, as noted in 5 and 4 Understanding these phases helps track fertility, explain menstrual symptoms, and identify potential reproductive issues. The most recent and highest quality study, 3, provides valuable insights into the roles of LH, FSH, and testosterone in spermatogenesis and folliculogenesis, highlighting the complexity of these processes and the need for further research. However, for the purpose of this question, the key takeaway is that the menstrual cycle is a complex process involving the interplay of multiple hormones and phases, and understanding these phases is essential for tracking fertility and identifying potential reproductive issues.