Vaginal micronized progesterone in continuous hormone replacement therapy. A prospective randomized study.

Background. In the non-hysterectomized postmenopausal woman undergoing estrogen replacement therapy, the co-administration of a progestogen is mandatory to counteract the estrogenic proliferative effect on the endometrium. Metabolic and tissue effects of the various progestins vary with dosage and route of administration. This study was performed to evaluate the effects of selected progestins on the lipidic profile and endometrial morphology. Methods. This is a prospective randomised study including 60 post-menopausal women undergoing hormonal replacement therapy (HRT). All patients received transdermic ethinil-estradiol in a continuous schedule. The utilized progestogens were: medroxyprogesterone acetate (MPA) 10 mg p.o. 12 days/month, transdermic nor-ethisterone acetate (NETA) 0.25 mg integrated in the ethinil-estradiol patches for the last two weeks of each cycle, micronized progesterone (MP) 100 mg transvaginally 12 days/month. Results. None of the tested protocols significantly altered the lipidic profile of this group of patients. We noticed different effects on the estrogen stimulated endometrium elicited by the different progestinic regimens. While the cyclic administration of oral MPA or transdermic NETA more frequently resulted in endometrial atrophy, the trans-vaginal administration of MP more often induced (p<0.005 at sixmonth and p <0.001 after 1 year) a functionallike secretive endometrium. Conclusions. Micronized progesterone, cyclically administered in the form of a vaginal cream, offers an acceptable and effective alternative for women on continuous HRT wishing to maintain their monthly cycle.