Hormones and Your Menstrual Cycle

A woman's menstrual cycle (monthly period) is controlled by changing levels of certain hormones. These hormones travel through the blood. Two hormones, estrogen and progesterone, play a big role in the menstrual cycle. They are produced in the ovaries (where eggs are stored).

The Menstrual Cycle

Hormones help prepare the uterus for pregnancy. At the start of the cycle, the two ovaries produce estrogen. This makes one ovary release an egg, and signals the production of progesterone. The egg travels through the fallopian tube. Then it enters the uterus. If the egg is fertilized, a woman becomes pregnant. If this doesn't happen, the egg is shed along with the uterine lining. This bleeding is called menstruation.