What is the primary female hormone that regulates the menstrual cycle?

The primary female hormone that regulates the menstrual cycle is oestrogen. This hormone plays a crucial role in the development and regulation of the female reproductive system and secondary sexual characteristics. In the menstrual cycle, oestrogen levels rise and fall at different phases, particularly in the follicular phase leading up to ovulation.

During this time, oestrogen is responsible for thickening the lining of the uterus in preparation for a potential pregnancy, and it also has a key role in modulating other hormones and bodily functions associated with the menstrual cycle. The peak of oestrogen coincides with ovulation, further indicating its crucial role in this periodic physiological process.

Other hormones like progesterone also play an important part, primarily after ovulation and in maintaining the uterine lining for potential pregnancy. However, oestrogen's role before and during ovulation makes it the primary hormone associated with the regulation of the menstrual cycle itself.