Abstract
Background. To study the role of progesterone (P4) in the regulation of circulating leptin in early human pregnancy, we measured the levels of leptin before and after administration of the antiprogestin mifepristone, followed by misoprostol in early pregnancy. Methods. Thirty-four women requesting termination of pregnancy, with ≤63 days of amenorrhea, received 200 mg of mifepristone on day 0, followed by either oral or vaginal administration of 0.8 mg of misoprostol on day 2. Five serial serum samples were assayed for leptin, human chorionic gonadotrophin (hCG), P4, estradiol (E2), cortisol, and mifepristone. Results. Circulating leptin concentrations decreased by 8.7 ± 29.7% (mean ± standard deviation) ( p < 0.05) following the ingestion of mifepristone. After misoprostol administration on day 2, a decrease of 12.6 ± 17.0% ( p < 0.05) was followed by a rebound on day 3 to 87.6 ± 25.7% of the pretreatment values. Two weeks after mifepristone, leptin levels had declined by 25.4 ± 30.4%. In contrast, E2, P4, and hCG concentrations continued to increase following mifepristone, followed by rapid declines from day 2 to day 3. Serum cortisol concentrations increased by 89.7% ± 82.7% in response to mifepristone, but this increase did not correlate with the decrease in leptin. The decrease in leptin levels on day 2 correlated with the decreases in P4 ( r = 0.37, p < 0.05) and in E2 ( r = 0.44, p < 0.05) levels. Conclusions. The fall in leptin levels following mifepristone implies a role for P4 in the regulation of leptin in early pregnancy. Moreover, the significant correlation between the changes in leptin and those of P4 and E2 at the time of luteolysis suggests that corpus luteum may also play a role in the regulation of circulating leptin in early pregnancy.