Is Menest Bioidentical or Synthetic?

Menest (esterified estrogen) is an FDA-approved drug used in hormone replacement therapy for treating symptoms of menopause such as hot flashes, itching, burning and dryness. It is also used to treat low estrogen levels due to other conditions and in some cases breast or prostate cancer. Menest is not a bioidentical hormone.

Bioidentical hormone replacement therapy gained popularity as an alternative for women after the suspension in 2002 of the Women's Health Initiative Trial of combined estrogen and progestin because of users' higher risk of breast cancer, heart disease, stroke and blood clots.

Misconceptions

• Bioidentical hormone therapy is sometimes referred to as "natural hormone therapy." The term "natural" can be misleading when used in conjunction with hormones, however.

  Bioidentical hormones are synthesized from yams and soy. They are considered more natural than other hormones used in hormone replacement therapy because they are chemically identical to the hormones made in women's bodies and act the same way in the body.

  As "Harvard Women's Health Watch" discusses in an Aug. 2006 article, components of other hormones, such as the pregnant mare's urine used in Premarin and the plants used in Cenestin, are natural, but these drugs are not bioidentical to human estrogen.

Menest Components

• According to the FDA monograph, esterified estrogens is "a mixture of the sodium salts of the sulfate esters of the estrogenic substances, principally estrone, that are of the type excreted by pregnant mares." Esterified estrogens contains 75 to 85 percent of sodium estrone sulfate and six to 15 percent of sodium equilin sulfate.

  Both the estrone and the equilin in Menest are synthesized from yams and soy.

Definition of Terms

• The term "synthetic hormone" is frequently used for non-bioidentical hormones to distinguish them from bioidentical hormones although both hormones are "synthesized" from plants. On the other hand, manufactured drugs that are not derived from natural sources may be no less safe despite being "synthetic." Comparative safety can only be determined by long-term studies.

Safety

• According to the "Harvard Women's Health Watch" article, whether bioidenticals are safer than other hormones is unknown since "few large studies have investigated the differences among the various hormones and methods of administration."

  In a Jan. 16, 2009 "WebMD Health News" article, Erika Schwartz, MD called for large-government-sponsored comparison studies.

Solution

• Until these studies happen, whether to use bioidentical or nonbioidentical hormones depends on the patient's own comfort and what will work best for her lifestyle as determined in consultation with her doctor.