Effect of different cyclical sequential progestins on endometrial vascularity in postmenopausal women compared with...

The effect of trimegestone-based and norethisterone-based hormone replacement therapy (HRT) regimens on the endometrial vascularity compared with that of the endometrium of the natural cycle were evaluated using immunohistochemical techniques. Endometrial vascular space area, diameter and number were defined in the functionalis layer of the endometrial samples from postmenopausal women who either completed a randomized, double blind, dose-ranging study of continuous oral micronized oestradiol 2 mg daily with trimegestone 0.05, 0.1, 0.25 and 0.5 mg/day from day 15-28 for six treatment cycles or were given cyclical sequential norethisterone (NET)-based HRT together with continuous 2 mg oral oestradiol valerate for three cycles. The control samples were LH-dated endometrial biopsies. NET-based HRT was associated with a higher number of smaller vascular spaces compared with the trimegestone-treated endometrium or that of the natural cycle. There was no dose-dependent effect in the four dose groups of trimegestone. In conclusion, norethisterone may exert a different effect on angiogenesis to that of trimegestone on endometrial vascular development.