The first group received continuous combined oral HRT containing 1mg 17-estradiol and 0.5 mg norethisterone acetate ( n = 39 ) , and the second group received sequential transdermal HRT releasing 50g/day estradiol alone given twice a week on days 1-14 and 50g/day estradiol plus 0.25 mg/day norethisterone acetate given twice a week on days 15-28 ( n = 37 ) .