Insulin sensitivity during postmenopausal hormone replacement with transdermal estradiol and intrauterine levonorgestrel

Background. The study was devised to measure the effect of intrauterinely d elivered levonorgestrel and transdermal estradiol on insulin sensitivity in postmenopausal women and compare this effect with that induced by transder mal estradiol alone. Methods. An open, prospective, comparative study of healthy postmenopausal women without earlier use of hormone replacement therapy. The estrogen ther apy group consisted of eight hysterectomized women, who used a transdermal patch delivering a daily dose of 50 mu g of estradiol continuously for 6 mo nths. The estrogen-progestin therapy group consisted of 13 women with an in tact uterus, who received a simultaneous combination of a transdermal patch and a levonorgestrel (20 mu g/day) intrauterine system for the same length of time. Fasting plasma concentrations of glucose, insulin and C-peptide a nd an insulin tolerance test were used to measure glucose metabolism and in sulin sensitivity. Results. Neither therapy changed the fasting plasma levels of glucose, insu lin or C-peptide. Transdermal estrogen improved insulin sensitivity by 22%, as measured by an insulin tolerance test, while a small increase of 3.6% w as observed using the combination therapy. Conclusions. Transdermal estradiol improves insulin Sensitivity in healthy postmenopausal women. Combining intrauterine levonorgestrel to transdermal estradiol reverses this effect. This combination does not, however, seem to induce insulin resistance.