A study of combined continuous ethinyl estradiol and norethindrone acetate for postmenopausal hormone replacement

In a blinded, prospective, dose-response pilot study of continuous estrogen-progestin replacement therapy, 77 thin, nonsmoking, white women, who were 12 to 60 months postmenopausal and had normal medical histories, were randomly assigned to receive one of five dose combinations of daily ethinyl estradiol and norethindrone acetate (20 micrograms and 1.0 mg, 10 micrograms and 1.0 mg, 10 micrograms and 0.5 mg, 5 micrograms and 1.0 mg, and 5 micrograms and 0.5 mg) or conjugated estrogens 0.625 mg on days 1 to 25 and medroxyprogesterone acetate 10 mg on days 16 to 25. An additional 10 women meeting the same criteria served as a comparison group by taking calcium only. During 12 months of therapy, continuous users had significantly less vaginal bleeding and spotting than did sequential users. As compared with baseline values, bone metabolism and computerized tomographic measurements of vertebral trabecular bone density at month 12 indicated reduced bone turnover and increased density in hormone users. Endometrial biopsy specimens were negative for hyperplasia and neoplasia. The continuous ethinyl estradiol-norethindrone acetate tablet, even at the lowest doses studied, provided the same salutary effects on bone, endometrium, and postmenopausal symptoms as sequential therapy while minimizing annoying vaginal bleeding and spotting.