October 9, 2013
Type of Oral Hormone Therapy Affects VT Risks in Postmenopausal Women

Seattle—When it comes to risk for venous thrombosis, the type of oral hormone therapies used by postmenopausal women can make a critical difference, according to a new study.

The new study published online by JAMA Internal Medicine, found that the oral hormone therapy conjugated equine estrogens (CEEs) showed an association with increased risk for venous thrombosis and possibly myocardial infarction, when compared with the hormone therapy oral estradiol.

“In an observational study of oral hormone therapy users, CEEs use was associated with a higher risk of incident venous thrombosis and possibly myocardial infarction than estradiol use,” the authors write. “This risk differential was supported by biologic data.”

CEES are derived from the urine of pregnant mares, while estradiol is a “natural” or “bioequivalent” estrogen, according to the study, which also noted that the cardiovascular safety of the hormone therapy (HT) products has not been established.

“Although oral estrogens are effective for managing menopause symptoms, not enough is known about the cardiovascular safety of different oral hormone therapy products relative to each other,” said first author Nicholas L. Smith, PhD, a professor of epidemiology at the University of Washington School of Public Health in Seattle and director of the Veterans Affairs (VA) Seattle Epidemiologic Research and Information Center (ERIC).

The study involved 384 postmenopausal women ages 30 to 79, who were members of the Group Health Cooperative, a large health maintenance organization in Washington State, and were on oral hormone therapy.

The researchers focused on 68 women who had venous thrombosis, 67 with myocardial infarction and 48 with ischemic stroke, comparing them to 201 matched controls.

The study found that, in adjusted analyses, current oral CEEs use compared with current oral estradiol use was associated with an increased venous thrombosis risk (odds ratio, 2.08; 95% CI, 1.02-4.27; P = .045) and an increased myocardial infarction risk that did not reach statistical significance (odds ratio, 1.87; 95% CI, 0.91-3.84; P = .09). There was no association with ischemic stroke risk (odds ratio, 1.13; 95% CI, 0.55-2.31; P =.74), according to the report.

An additional finding was that, among 140 controls, CEEs users compared with estradiol users had higher endogenous thrombin potential–based normalized activated protein C sensitivity ratios (P < .001), indicating a stronger clotting propensity.

“The findings of this comparative safety investigation need replication,” the authors write. “If confirmed, the results would provide valuable information to women and their health care professionals when making safety decisions regarding available HT options for menopausal symptom management.”

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