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Esterified estrogens (EEs) (brand names Amnestrogen, Estratab, Estratest, Evex, Femogen, Menest) are synthetic, plant-based estrogens that are manufactured from soybeans and yams. They are used in hormone replacement therapy for menopausal symptoms, female hypogonadism, ovariectomy, and primary ovarian failure and in the treatment of prostate cancer.
EEs consist primarily of sodium estrone sulfate and sodium equilin sulfate, and are very similar to conjugated equine estrogen (CEE) preparations such as Premarin. However, EEs and CEEs differ in the sources of their contents and in the percentages of their constituents; CEEs consist of approximately 53% sodium estrone sulfate and 25% sodium equilin sulfate, while EEs contain approximately 80% sodium estrone sulfate and 11% sodium equilin sulfate. EEs and CEEs have been found to produce similar serum levels of estrone and estradiol. One study found that the risk of venous thrombosis may be less with EEs relative to CEEs.
Estratest is a combination formulation of 1.25 mg EEs with 2.5 mg methyltestosterone.