Which hormone primarily regulates the menstrual cycle?

The primary hormone regulating the menstrual cycle is estrogen. Estrogen is pivotal in the development and regulation of the menstrual cycle and is primarily produced by the ovaries. Throughout the menstrual cycle, estrogen levels fluctuate, with the most significant rise occurring during the follicular phase, leading up to ovulation. This increase in estrogen stimulates the thickening of the endometrial lining in preparation for a potential pregnancy.

Estrogen not only promotes the growth of the uterine lining but also regulates the secretion of other hormones, including luteinizing hormone and follicle-stimulating hormone, from the pituitary gland, which further coordinates the cycle. The interplay between estrogen and these hormones ensures the cycle progresses correctly, facilitating ovulation and preparing the body for possible conception.

In addition to estrogen, progesterone plays a critical role post-ovulation by preparing the endometrium for implantation, but it does not primarily regulate the menstrual cycle. While luteinizing hormone is crucial for regulating ovulation and other aspects of the menstrual cycle, estrogen remains the primary hormone influencing the cyclical changes in the uterine lining and overall hormonal balance. Oxytocin is more involved with uterine contractions during labor and lactation and is not a primary regulator of the menstrual cycle.