The influence of norethisterone acetate on urinary urodilatin excretion in postmenopausal women.

We have previously found that transdermal estradiol application significantly stimulated the urinary excretion of urodilatin, a newly discovered renal peptide with diuretic properties. It is well established that the addition of progestogen is necessary in hormone replacement therapy in women with an intact uterus. This study was designed specifically to examine the effect of progestogen norethisterone acetate (NETA) in postmenopausal women. NETA given alone orally in dosages of 1 mg/d and 2 mg/d for 10 days, as used for the progestogen-challenge test, did not increase urodilatin excretion. NETA in combination with estradiol, administered orally and transdermally in the second half of a 4-week estradiol treatment cycle, did not significantly change urodilatin excretion. The results of the present study indicate that NETA addition to estrogen replacement therapy may antagonize the stimulating estradiol effect on urodilatin production as registered in our earlier study.