Administration of an antiprogesterone up-regulates estrogen receptors in the endometrium of women using Norplant: a pilot study.

OBJECTIVE

To determine the effect of a single dose of mifepristone (200 mg) on endometrial estrogen and progesterone receptors in Norplant users.

DESIGN

A prospective single-blind placebo-controlled pilot study. SETTING; Women were recruited from a large family planning clinic and were studied either at the clinic or in a clinical research unit attached to a teaching hospital gynecology department.

PATIENT(S): Eight women using Norplant and experiencing vaginal bleeding more often than once every 24 days. All completed the study.

INTERVENTION(S): Endometrial biopsies were taken after treatment with both placebo and 200 mg of mifepristone, both given at the start of a bleeding episode.

MAIN OUTCOME MEASURE(S): Expression of endometrial progesterone (PR) and estrogen (ER) receptors, ovulation, and vaginal bleeding.

RESULT(S): Mifepristone administration was associated with down-regulation of PR receptor subtype B and up-regulation of ER. Women treated with mifepristone showed a tendency to increased ovulation rates and reduced vaginal bleeding.

CONCLUSION(S): The effect of mifepristone on endometrial steroid receptors was consistent with functional inhibition of progesterone. The findings warrant further investigation of this regimen as a strategy to reduce frequent bleeding.