We performed a pharmacodynamic comparison of human urinary follicle-stimulating hormone (hFSH) and human menopausal gonadotropin (hMG) to characterize differences in the bioavailability of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), as well as to compare estrogen responses in normal women and those with polycystic ovary syndrome (PCOS). Ten women with PCOS and ten normal ovulatory controls were randomized to receive a single dose (2 ampules) of either hFSH or hMG. Serum LH decreased significantly following hFSH with responses occurring earlier in controls (24.5 +/- 10.9% after 30 minutes) than in PCOS patients (27.3 +/- 7.5% after 18 hours). After hMG, LH increased only in controls (33.8 +/- 16.3%). An FSH increment following hFSH was observed in both PCOS patients (54.7 +/- 24.8%) and controls (74.6 +/- 36.8%), with peak responses at 6 and 4 hours, respectively. However, after hMG, FSH increased only in controls. The LH/FSH ratio after hFSH decreased, with the nadir at 18 hours (1.438 +/- 0.183) being similar to baseline LH/FSH ratios of controls (1.433 +/- 0.341). Serum estradiol (E2) increased following hMG, with peak responses after 18 hours, in both PCOS patients (75.4 +/- 28.6%) and controls (88.5 +/- 32.5%). The peak E2 response to hFSH was observed to be earlier in PCOS patients (147 +/- 34%), occurring after 12 hours, compared with controls (58 +/- 29% after 18 hours).