Major Hormone Therapy Studies

There are several important studies that provide valuable information for women and their healthcare providers about the risks and benefits of hormone therapy.

1976-present Nurses' Health Study (NHS)

The single largest cohort study of women, the ongoing NHS was established in 1976 to study the relationship between oral contraceptive use and cigarette smoking and risk of major illnesses. The scope and range has since broadened to include implications of various lifestyle factors (i.e. exercise and diet) on women's health. Initially comprised of 127,000 nurses, 30 to 55, participants receive detailed questionnaires every 2 years in which they report medical histories, daily diet habits and major life events that have occurred in the previous 24 months.

Response rate averages 90 percent. Major findings include:

• Birth control pills do not increase non-smoking women's risk of heart disease
• Women who take oral contraceptives for more than 5 years have less than half the risk of ovarian cancer than women who have never used birth control pills
• Women who take estrogen after menopause decrease risk of heart disease, but raise risk of breast cancer.

For more information, click here.

1987-1990 Post-menopausal Estogen/Progestin Interventions (PEPI) Trial

This three-year study involved 875 postmenopausal women aged 45 to 64 years. 32% previously had a hysterectomy. The study's purpose was to test the effects of estrogen therapy on four factors that affect a woman's risk of heart disease: HDL (good) cholesterol, systolic blood pressure, fibrinogen and insulin.

Women were randomly assigned to five treatment groups:

1. A placebo (no hormone)
2. Estrogen (0.625 mg Premarin)
3. Estrogen (0.625 mg Premarin) and progestin (2.5 mg Provera) taken daily
4. Estrogen (0.625 mg Premarin) taken daily and progestin (10 mg) taken 12 days each month
5. Estrogen (0.625 mg Premarin) and micronized progesterone (200 mg progesterone USP) taken daily.

In the study, all of the estrogen/progestin combinations produced significantly greater increases in HDL (good) cholesterol levels than the placebo. Estrogen combined with natural, micronized progesterone provided the best cardiovascular protection of all the combined regimens, nearly equal to taking estrogen alone. Combining estrogen with progesterone or progestin was shown to help protect women against endometrial cancer. The study also discovered postmenopausal women taking hormones gained less weight than if not taking hormones.

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1995-1998 Heart and Estrogen/Progestin Replacement Study (HERS)

This three year study of 2,300 postmenopausal women with coronary heart disease (CHD) studied the role of hormone therapy on heart disease risk. After 6.8 years, those randomly assigned to take supplemental estrogen and progestin showed no cardiovascular benefi t or harm. The study recommended women not start estrogen/progestin to prevent future heart attacks, but if already using estrogen therapy, to continue as there may be a long-term benefi t. Results of the 1998-2002 HERS II follow-up study concluded that postmenopausal with CHD not use combination hormone therapy to reduce the risk of CHD events, such as heart attacks.

1991-2005 Women's Health Initiative Study (WHI)

Involving over 161,000 women ages 50-79, the WHI had two components. The primary component, a randomized controlled trial on hormone therapy in postmenopausal women with breast cancer as a primary endpoint, had three arms.

1. Administration of oral, single dose Prempro synthetic estrogen and progestin
2. Administration of oral, single dose Premarin synthetic estrogen
3. Administration of calcium/vitamin D to evaluated the effect on prevention of osteoporosis related fractures and colorectal cancer. The second component examined the relationship between lifestyle, health and risk factors and specific disease outcomes. This 15-year project ended March 2005.

For complete information and study results, click here.

For additional information about hormone therapy, please contact Women's Health America at This e-mail address is being protected from spambots, you need JavaScript enabled to view it or call 800.558.7046.