Effects of progesterone administered by nasal spray on the human postmenopausal endometrium

The aim of the study was to assess the effectiveness of progesterone (P) administered by nasal spray (NS) in inducing secretory changes within estrogen and non-estrogen primed postmenopausal endometrium. Ten healthy post-menopausal women before vaginal hysterectomy for prolapse were randomly treated by either oral estrogens for 3-4 weeks combined for the last 5-7 days with nasally administered P at the daily dose of 34 mg, or by only P for 6 days. Endometrial samples were taken before P administration and 8 h after the last dose. In the group not treated with estrogens, P did not induce significant secretory changes in any case except one which showed a proliferative endometrial pattern at the first evaluation. In the group treated with estrogens, in all the cases after P administration clear secretory changes (abundant vacuoles, endoluminal secretion) occurred. It is possible to conclude that P administered by NS exerts an end-organ effect within the endometrium of postmenopausal women pretreated with estrogens.