Which hormone is listed as involved in the menstrual cycle?

• A. Gonadotropin-releasing hormone (GnRH)
• B. Insulin
• C. Adrenaline
• D. Melatonin

Answer: (A)

Regulation of the menstrual cycle is driven by a hormonal cascade that starts in the brain. The hypothalamus releases gonadotropin-releasing hormone in regular pulses. This signal prompts the anterior pituitary to secrete the gonadotropins FSH and LH. FSH stimulates ovarian follicle growth, while LH triggers ovulation and supports the corpus luteum; the ovaries then produce estrogen and progesterone that shape the cycle and provide feedback to the hypothalamus and pituitary to modulate further release. The pulsatile nature of GnRH is crucial: the pattern of release controls how much FSH and LH are produced, which in turn governs the timing of ovulation and the overall cycle.

Other hormones listed have important roles in different body systems—insulin for glucose regulation, adrenaline for the stress response, and melatonin for sleep-wake cycles. They are not the primary drivers of the menstrual cycle.