Which hormone is primarily responsible for regulating the menstrual cycle?

• A. Testosterone
• B. Estrogen
• C. Progesterone
• D. Luteinizing Hormone

Answer: (B)

Estrogen plays a pivotal role in regulating the menstrual cycle, primarily influencing the growth and maturation of the ovarian follicles. During the first half of the cycle, known as the follicular phase, estrogen levels begin to rise as the developing follicles produce this hormone. Elevated estrogen is crucial as it stimulates the proliferation of the endometrial lining in preparation for a potential implantation of an embryo.

Additionally, estrogen has a significant effect on the hypothalamic-pituitary axis. Its surge just before ovulation leads to a spike in luteinizing hormone, which triggers the release of the ovum from the dominant follicle. This cycle of rising and falling estrogen levels is a key driver of the hormonal changes that occur throughout the menstrual cycle, making it the primary hormone responsible for its regulation.