Several key hormones orchestrate the menstrual cycle, directly impacting menstruation. These include:
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Estrogen: Estrogen levels fluctuate throughout the cycle. They rise during the follicular phase, peak before ovulation, and then decrease sharply before menstruation begins (as noted in sources like the Merck Manual and HelloClue). This drop in estrogen is often associated with premenstrual symptoms.
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Progesterone: Progesterone levels increase after ovulation, preparing the uterine lining for a potential pregnancy. If pregnancy doesn't occur, progesterone levels drop, triggering menstruation. HelloClue highlights the role of prostaglandins, whose levels rise after ovulation and peak during menstruation, causing uterine cramping.
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Luteinizing Hormone (LH): LH triggers ovulation, the release of an egg from the ovary. A surge in LH occurs mid-cycle. Merck Manual details how this surge precedes ovulation by 16 to 32 hours.
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Follicle-Stimulating Hormone (FSH): FSH stimulates the growth of follicles in the ovaries, each containing an egg. West Suburban Medical Center lists FSH as a key player in the menstrual cycle. Levels are highest at the beginning of the cycle.
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Gonadotropin-releasing Hormone (GnRH): GnRH, released from the hypothalamus, regulates the release of LH and FSH from the pituitary gland. This acts as the primary initiator of the hormonal cascade that drives the menstrual cycle, as mentioned by West Suburban Medical Center.
In short, the interplay of these hormones governs the preparation of the uterus for pregnancy and the shedding of its lining during menstruation. The cyclical changes in these hormone levels are crucial to the monthly processes associated with the menstrual cycle. Hormonal imbalances can disrupt this cycle, leading to irregular periods or other issues.
