What is the Effect of FSH on Egg Formation?

During a woman's menstrual cycle, follicle stimulating hormone (FSH) stimulates the formation of an egg from the follicles of the ovaries.

Background

• When a woman is born, she has about one million to two million immature eggs, or follicles, in her ovaries. About midway through a woman's menstrual cycle, her pituitary gland secretes FSH to stimulate egg development.

Ovulation

• After the FSH stimulates egg development, the egg follicle secretes estrogen, which tells the lining of the uterus to get ready for a fertilized egg. As estrogen increases and FSH decreases, the pituitary gland secretes luteinizing hormone (LH) to finish developing the egg and release it from the ovary (ovulation).

After ovulation

• After ovulation, the pituitary gland secretes luteotrophic hormone (LTH), causing a tissue called corpus luteum to form in the uterus. As the corpus luteum releases increasing amounts of progesterone, the pituitary gland significantly decreases the release of FSH and LH.

FSH and menopause

• Because the pituitary gland secretes FSH in response to low estrogen levels, FSH levels increase as a woman approaches menopause.

Considerations

• Most follicles die during a woman's reproductive life. With each menstrual cycle, a woman loses 1,000 follicles and only one follicle matures into an egg.