Circulating luteinizing hormone pulse frequency in women with polycystic ovary syndrome.

To determine whether pulsatile LH frequency is altered in patients with the polycystic ovary syndrome (PCO) serum LH was measured every 10 min for 12 h (0800-2000 h) in nine patients. Six cycling women studied in the midfollicular (MF) or early follicular (EF) phases of their cycle served as controls. Three of these women were studied in both phases, yielding a total of nine control studies. In the PCO patients the mean LH pulse frequency was 12.1 +/- 0.7 (+/- SE) pulses/12 h. This value was indistinguishable from that of normal EF (12.1 +/- 0.4 pulses/12 h) or MF women (12.0 +/- 0.7 pulses/12 h). In contrast, the mean LH pulse amplitude in the PCO patients (12.2 +/- 2.7 mIU/mL) was higher (P less than 0.05) than that in normal women in either phase (EF, 6.2 +/- 0.8 mIU/mL; MF, 6.4 +/- 0.6 mIU/mL). These results suggest that the elevations in serum LH levels that occur in PCO patients are due primarily to increased LH pulse amplitude rather than increased pulse frequency.