The ovaries have 200,000 - 400,000 follicles, tiny sacks that contain the materials needed to produce mature eggs, or ova. The ovaries produce two major female hormones: estrogen and progesterone.
Estrogen. Estrogens have an effect on about 300 different tissues throughout a woman's body:
- They are essential for the reproductive process and the development of the female organs.
- Estrogens determine the characteristic female distribution of body fat on the hips and thighs, which develops during adolescence.
- They also are involved in tissues in the central nervous system (including the brain), the bones, the liver, and the urinary tract.
Estrogen has different forms:
- The strongest form is estradiol.
- The other important, but less powerful, estrogens are estrone and estriol.
Most of the estrogens in the body are produced by the ovaries, but they can also be formed by other tissues, such as body fat, skin, and muscle.
Progesterone. Progesterone, the other major female hormone, is necessary for thickening and preparing the uterine lining for the fertilized egg.
Menopause and Perimenopause
Review Date: 07/26/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.