The ovaries produce two major female hormones, estrogen and progesterone . Estrogens are a group of female hormones essential for the reproductive process and for the development of the uterus, breasts, and other physical changes associated with puberty. Estrogens determine the characteristic female distribution of body fat on the hips and thighs, which develops during adolescence. The other important, but less powerful, estrogens are estrone and estriol . Although most of the estrogens in the body are produced by the ovaries, they can also be formed by other tissues, such as body fat, skin, and muscle.
Progesterone is necessary for thickening and preparing the uterine lining for the fertilized egg.
As a woman ages, her supply of eggs declines. Menopause is defined as the ending of menstrual cycles and occurs naturally when the woman's supply of follicles has been depleted or if the ovaries are surgically removed. The ovarian secretion of estrogen and progesterone ends with menopause. The process is not sudden, however. A period called perimenopause usually begins a few years before the last menstrual cycle and may last for a few years.