Lipid effects of an intrauterine levonorgestrel device or oral vs. vaginal natural progesterone in postmenopausal women treated with percutaneous estradiol

Background: The ideal progestin for combined hormone replacement therapy should be free of adverse effects on lipid metabolism. We therefore examined lipid profiles during continuous hormone replacement therapy (HRT) with an estradiol-gel combined with either a levonorgestrel-releasing intrauterine device (LNG-IUD) or oral/vaginal natural progesterone. Methods: Sixty menopausal women recruited in this open, non-randomised parallel three-group study received percutaneous gel containing 1.5 mg of estradiol daily. Progestin was administered to the women with an LNG-IUD (n = 20), as oral natural progesterone (n = 21) 100 mg daily on the 1 - 25 calendar days of the month or as vaginal progesterone (n = 19) 100 - 200 mg daily on the 1 - 25 calendar days of the month. Serum concentrations for total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides and sex hormone binding globulin (SHBG) were measured at 0, 6 and 12 months. The median (and 95% confidence interval) of the serum SHBG, total, LDL-, HDL-cholesterol and triglycerides concentrations at baseline and after 6 and 12 months of the study and the ratio of 6 and 12 months values to baseline values were calculated. Results: Total cholesterol was significantly decreased (8%) in the vaginal progesterone group at the end of the trial. HDL-cholesterol did not change in either of the progesterone groups, while a slight but transient decrease (median 15%) was seen at 6 months in the LNG-IUD group. There were no significant changes in triglycerides or LDL-cholesterol concentrations in any group. SHBG did not change significantly in the LNG-IUD and vaginal progesterone groups, while a slight but transient increase was seen in oral P group at 6 months. Conclusions: As the only significant harmful effect observed was a transient decrease in HDL-cholesterol in the LNG-IUD group at 6 months, each of these HRT-administration methods can be regarded as being safe in their effects on lipid metabolism.