Progesterone inhibition of the hypothalamic gonadotropin-releasing hormone pulse generator: evidence for varied effects in hyperandrogenemic adolescent girls.

Compared with normal women, adults with polycystic ovarian syndrome (PCOS) require higher progesterone (P) concentrations to inhibit GnRH (LH) pulse frequency, which contributes to persistently rapid GnRH pulses and elevated LH levels in PCOS. To explore the origin of this abnormality, we assessed hypothalamic sensitivity to P feedback in nine normal controls and 11 hyperandrogenemic (HA) adolescents. Subjects first underwent frequent blood sampling for 11 h to assess baseline LH pulse frequency. Thereafter, oral estradiol and micronized P were given for 7 d to achieve mean estradiol and P levels of 143 +/- 16 pg/ml (524 +/- 60 pmol/liter) and 7.8 +/- 0.7 ng/ml (24.9 +/- 2.3 nmol/liter), respectively. LH pulse frequency was then reassessed. On d 7, the slope of the percent reduction of LH pulses per 11 h as a function of the d 7 P concentration was less in the HA group compared with controls (P = 0.02) despite similar P levels. LH pulse frequency was suppressed in all NC (mean, 7.0 to 3.4 pulses/11 h), but was unchanged in six of the HA girls (mean, 8.3 to 7.5 pulses/11 h). In contrast, in the other five HA adolescents, P induced similar slowing of LH pulses to that seen in NC (mean, 10.0 to 5.0 pulses/11 h). Baseline free testosterone levels were similar in both HA groups; the only observed difference between these HA groups is that the P-suppressible subjects were all of Hispanic descent. These data suggest that hyperandrogenemia during adolescence is variably associated with decreased sensitivity to P, which may have a partially genetic basis.