Question

Describe hormonal control in various phases of menstrual cycle.

Hint:

Negative feedback (estrogen/progesterone) and positive feedback (LH surge) tightly regulate the menstrual cycle.

Answer 1

The menstrual cycle (~28 days) is regulated by hormones across four phases: 1. Menstrual phase (Days 1–5): Low estrogen and progesterone (due to corpus luteum degeneration) cause uterine lining (endometrium) shedding. Follicle-stimulating hormone (FSH) from the pituitary begins stimulating follicle growth. 2. Follicular phase (Days 1–13): FSH promotes ovarian follicle development, which secretes estrogen. Estrogen thickens the endometrium and triggers a luteinizing hormone (LH) surge. 3. Ovulatory phase (Day 14): LH surge induces ovulation (egg release from the mature follicle). Estrogen peaks, and the follicle transforms into the corpus luteum. 4. Luteal phase (Days 15–28): Corpus luteum secretes progesterone and some estrogen, maintaining the endometrium for potential implantation. If no pregnancy occurs, the corpus luteum degenerates, hormone levels drop, triggering menstruation.