Effects of an intranasally administered low dose progestogen on the pituitary and gonadal functions.

This study was undertaken to investigate possible mechanisms of action of a daily intranasally administered low dose of norethisterone acetate (40 microgram) in regularly menstruating young women. Besides measurement of basal body temperature, serum concentrations of FSH, LH, estradiol and progesterone were determined over one treatment cycle. An endometrial biopsy was taken on day 27 or 28 of the cycle. In spite of a considerable individual variation in the respective values the following effects could be observed: In 8 of 9 subjects the midcycle LH peak was abolished, while basal FSH and LH levels remained within the control range of the follicular and luteal phases. A variable reduction of progesterone levels below the range indicative of a normal luteal phase function suggested a tendency to atypical corpus luteum formation. In 8 of 9 endometrial biopsies, however, secretory transformation could be found.