Transdermal 17-β-Estradiol and Risk of Developing Type 2 Diabetes in a Population of Healthy, Nonobese Postmenopausal Women

OBJECTIVE: Various observational and randomized studies have demonstrated a reduction in the incidence of type 2 diabetes in postmenopausal women who received estrogen orally. No studies have been performed on the incidence of type 2 diabetes in postmenopausal women treated with transdermal 17-beta-estradiol. The purpose of our study was to assess the influence of transdermal 17-beta-estradiol on the incidence of type 2 diabetes in a population of healthy, nonobese postmenopausal women. RESEARCH DESIGN AND METHODS: Between January 1998 and December 2002, 673 healthy, nonobese postmenopausal women (mean age 54 +/- 5 years) were enrolled: 144 (21.4%) of these took transdermal 17-beta-estradiol and 529 (78.6%) had never taken hormones during their postmenopausal period. Final elaboration of the data took place in July 2003, with a mean follow-up of 3.7 +/- 0.7 years (ranging from 0.5 to 5 years). RESULTS: Type 2 diabetes developed in 60 patients during the follow-up period, which is the equivalent of 22 cases per 1,000 women-years. In the "hormones nonusers" group, diabetes developed in 10% (54 of 529 women; equivalent of 26.5 cases/1,000 women-years), whereas in the "hormones users" group, diabetes developed in 4.16% (6 of 144 women; equivalent of 12.1 cases/1,000 women-years). Transdermal 17-beta-estradiol emerged as a treatment that significantly reduced the risk of developing diabetes (RR 2.19, 95% CI 1.79-3.56; P=0.006). CONCLUSIONS: Our results suggest a significant reduction in the incidence of type 2 diabetes in our population of nonobese, healthy postmenopausal women who used transdermal 17-beta-estradiol. This could suggest that, in some women, the estrogen deficiency that occurs after menopause could represent a fundamental step in the process of diabetogenesis.