If the egg is not fertilized, the corpus luteum degenerates to a form called the corpus albicans, and estrogen and progesterone levels drop. Finally, the endometrial lining sloughs off and is shed during menstruation. Beginning of menstruation to end of blood flow. Estrogen and progesterone start out at their lowest levels. FSH levels rise to stimulate maturity of follicles.
Ovaries start producing estrogen and levels rise, while progesterone remains low.
Largest follicle bursts and releases egg into fallopian tube. Progesterone and estrogen levels rise. Corpus luteum continues to produce estrogen and progesterone. Estrogen and progesterone levels drop. The blood vessel lining sloughs off and menstruation begins.