Increased luteinizing hormone pulse frequency in obese oligomenorrheic girls with no evidence of hyperandrogenism.

OBJECTIVE: To determine whether obese, nonhirsute adolescents with oligomenorrhea exhibit similar increased LH pulse secretion patterns compared with obese girls with polycystic ovary syndrome (PCOS).
DESIGN: Prospective, observational study.
SETTING: Tertiary university hospital. PATIENT(S): Nine obese girls with oligomenorrhea, 15 with PCOS, and 10 controls. INTERVENTION(S): Twenty-four-hour IV blood sampling for LH (every 10 minutes); measurement of steroid hormones (every 12 hours); and injection of leuprolide acetate (10 microgm/kg SC). MAIN OUTCOME MEASURE(S): Twenty-four-hour, wake, and sleep LH mean serum concentration, pulse frequency, amplitude; steroid hormones, including free androgen index (FAI); and pre- and post-leuprolide acetate 17-hydroxyprogesterone measurements. RESULT(S): Twenty-four-hour LH pulse frequency in oligomenorrheic girls (18.6 +/- 1.2) (mean +/- SE) was comparable to that in girls with PCOS (20.9 +/- 0.7) and greater than in normal girls (13.4 +/- 0.8). The pulse number during both sleep and wake was identical in oligomenorrheic and PCOS girls and significantly greater than that of normal girls. Mean 24-hour LH level, serum androgen levels, and FAI in oligomenorrheic girls were equivalent to those of normal controls and lower than those of PCOS girls. CONCLUSION(S): These preliminary results indicate that obese girls with oligomenorrhea exhibit increased LH pulse frequency in the absence of clinical and/or biochemical evidence of hyperandrogenism.