Some adolescents with a history of idiopathic central precocious puberty (ICPP) develop hyperandrogenism. HYPOTHESIS: Luteinizing hormone (LH) hypersecretion could be a common mechanism underlying ICPP and polycystic ovary syndrome. AIM: To explore the GnRH-LH axis in those patients. DESIGN: To compare overnight LH secretion in 7 healthy adolescents (CG) with that in patients with prior ICPP [5 with (CPPA) and 7 without (CPPB) hyperandrogenism]. To analyze daytime LH secretion in those patients. METHODS: LH secretion was quantified by immunofluorometry and deconvolution analysis. RESULTS: Nighttime mean LH (international units/liter) was higher in CPPA (6.9 +/- 1.5) than in CPPB (3.2 +/- 0.4, p <0.05) and CG (2.9 +/- 0.4, p <0.01). Deconvolution analysis revealed a greater nighttime LH frequency (pulses/hour) both in CPPA (0.91 +/- 0.06, p <0.01) and CPPB (0.74 +/- 0.02, p <0.05) than in CG (0.45 +/- 0.07). CPPA patients maintained a higher frequency than CPPB. Pulsatile LH production was greater in CPPA than in CG (50 +/- 12 vs. 18 +/- 3 IU/l/day, p <0.01). Daytime mass of LH released per burst and pulsatile production rate were significantly greater in CPPA than in CPPB patients. CONCLUSIONS: Hyperandrogenic adolescents with prior ICPP show increased pulsatile LH secretion. Augmentation of LH pulsatility may predispose to or cause hyperandrogenism in some adolescents with a history of precocious puberty.