Introduction

Introduction

The ovaries contain between 200,000 and 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 for 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 most potent 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

As a woman ages, her supply of eggs declines. Menopause occurs naturally after the woman's supply of follicles has been depleted and menstruation ends completely. (Menopause may also be induced if the ovaries are surgically removed.)

Perimenopause. Menopause does not occur suddenly. A period called perimenopause usually begins a few years before the last menstrual cycle. Some experts believe there are three stages in the transition:

• Early Stage. The beginning of perimenopause can begin in some women in their 30s, but most often it starts between ages 40 and 44. It is marked by changes in menstrual flow and in the length of the cycle. There may be sudden surges in estrogen.
• Middle Stage. In the middle cycle, periods become irregular but they are not skipped.
• Late Stage. In the late stages, women begin missing the periods until they finally stop. About 6 months before menopause estrogen levels drop significantly. The fall in estrogen triggers the typical symptoms of vaginal dryness and hot flashes (which can last from half a year to more than 5 years after onset of menopause).