Physicians may prescribe a course of estrogen replacement therapy, or sometimes a low-dose oral contraceptive, for women who are troubled by perimenopausal symptoms.
Many researchers believe that hormone replacement therapy can also help protect women against heart disease and osteoporosis, conditions which estrogen helps control.
(Women who have had cancer or such conditions as heart, liver and gallbladder disease are often advised not to try HRT.)
The most commonly prescribed form of treatment uses both estrogen and progestin, a synthetic hormone similar to the natural female hormone progesterone.
Researchers believe that progestin protects the endometrium -- the lining of the uterus -- against the increased rate of cancer which using estrogen may present.
No one knows precisely what long-range benefits and risks accompany hormone replacement therapy.
However, the shorter-term benefits include reducing the number of hot flashes, decreasing urinary incontinence and increasing vaginal moisture, which makes intercourse less painful.
There are also side effects.
The following is a list published in "Estrogen Replacement Therapy: The Johns Hopkins Guide to Making an Informed Decision," a new booklet produced by the Johns Hopkins Women's Health Center.
(For details, call (410) 955-8660.)
* The side effects of estrogens include bloating and weight gain because estrogen can cause the body to retain salt and water; headaches; nausea; gallbladder symptoms; breast tenderness and enlargement.
* The side effects of progestins include mood changes -- usually described as mildly depressed -- and some pre-menstrual symptoms such as breast tenderness, food cravings and increased irritability.
* Sometimes women taking hormone replacement therapy will notice vaginal bleeding or spotting.
Some side effects may be minimized by adjusting the dosages of the medication.
Dr. Howard Zacur, co-author of the booklet and director of the Johns Hopkins Estrogen Consultation Service, says it can take a few days -- or several months -- for a woman to discover what regimen works best for her.