What are conjugated estrogens?

Marina Johnson
Endocrinology Diabetes & Metabolism

Conjugated estrogens are synthetic estrogens from either animals or plants that mimic the actions of natural human estrogen – estradiol. The most commonly prescribed form of hormone replacement therapy (HRT) in the United States is Premarin, which is conjugated horse estrogen. Cenestin and Enjuvia are synthetic hormones made from plant estrogens. They are both given as pills taken orally once a day.

Oral estrogens are convenient and easy to take, but they carry a higher risk of heart attacks and strokes. For menopausal women who still have their uterus, oral estrogen is combined with a synthetic progestin, medroxyprogesterone to protect against uterine cancer. This combination is marketed as Prempro and leads to an increased risk of breast cancer, dementia and incontinence.

A safer choice for HRT is estradiol that’s identical to the natural estrogen in a woman’s body. The increased side effects seen with oral pills can be avoided by giving estradiol topically as a patch, cream, gel or mist. Typical pharmaceutical forms of natural estrogen include: Vivelle patch, Divigel, Estrogel or Evamist. These are preferred to compounded hormones because they meet higher standards for quality control and effectiveness.

Conjugated estrogens are a patented blend of estrogens used in the pharmaceutical brands of medications typically used to treat the symptoms of menopause. They contain a mixture of water-soluble estrogens derived from natural sources -- estradiol from the urine of pregnant horses, estrone and equilin.

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