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WOMEN’S SEX HORMONES (1999)

According to a survey presented at the October 1998 meeting of the American Society for Reproductive Medicine, 64 percent of women couldn’t name the hormones that play a key role in reproduction. Of those surveyed, 44 percent said they didn’t know much about estrogen, and 65 percent didn’t know about progesterone.

For women approaching menopause, lack of knowledge about female hormones could make it difficult to decide about hormone replacement therapy (HRT). To help, here’s a refresher course in female hormones and what they do.

Sex hormones 101

Hormones are substances that carry chemical messages from one organ to another organ or to other tissues. Sex hormones work together in an intricate pattern to make the reproductive cycle function properly.

The major female sex hormones are estrogen and progesterone, which are produced mainly by the ovaries during the reproductive years. In addition, follicle-stimulating hormone (FSH) is produced by the pituitary gland, located at the base of the brain. FSH stimulates the granulosa cells of the follicles surrounding the eggs in the ovaries, causing them to produce estrogen.

When estrogen reaches a certain level, it cues the hypothalamus (in the brain) to secrete luteinizing hormone (LH). When LH peaks, the ovary releases an egg. The follicle then becomes a corpus luteum, which produces progesterone in addition to estrogen.

The hormones build up the lining of the uterus, preparing it for a possible pregnancy. If there’s no pregnancy, hormone production declines. When progesterone drops to a certain level, the lining of the uterus sheds, resulting in menstruation. The lower levels of estrogen and progesterone signal the production of FSH, and the cycle begins again.

One more thing: As a woman ages, her egg supply wanes. As a result, hormone levels begin to fluctuate. This signals the start of menopause.

Estrogen

Estrogen (estradiol) is the main female sex hormone. Besides shepherding a woman’s body through ovulation, conception and pregnancy, estrogen also maintains bone strength and may protect her cardiovascular system.

After menopause, estrogen production from the ovaries declines. Small amounts continue to be produced by fat cells. Estrogen production drops to about one-third of what it was during childbearing years. This drop in estrogen may lead to osteoporosis and heart disease. This is the primary reason doctors recommend estrogen replacement. Estrogen replacement protects against osteoporosis by strengthening bones and reduces the risk of heart disease by raising high-density lipoprotein (HDL) cholesterol (the good kind) and lowering low-density lipoprotein (LDL) cholesterol (the bad kind).

Progesterone

Progesterone works in concert with estrogen to prepare a woman’s body for conception and pregnancy. Progesterone helps regulate her menstrual cycle. When periods start to become irregular with the approach of menopause (perimenopause), progesterone plays a role. After menopause, a woman’s body produces only a small fraction of the progesterone it produced during her reproductive years.

(To see how hormone concentrations fluctuate during a woman’s monthly ovulation cycle, click on the graphic below.)

Taking synthetic progestogen (a form of progesterone) with estrogen causes the lining of the uterus to shed. If a woman takes estrogen, adding progestogen decreases her risk of endometrial cancer.

Androgen

Although androgen is commonly thought of as a male hormone, it’s also produced by a woman’s ovaries, adrenal glands and other tissues. Androgen gets part of the credit for the rapid growth spurt girls experience at puberty. During menopause, a woman might lose at least half of her androgen production — more if her ovaries have been removed. After menopause, adding androgen to HRT may help alleviate hot flashes in women who don’t get relief from them with estrogen.

Self knowledge

Understanding how her body works can help a woman make informed choices about how to care for it. As menopause approaches, understanding how hormones work becomes especially important.