CONICET | Buscador de Institutos y Recursos Humanos

To evaluate the androgen negative feed back in the control of LH secretion in eumenorrheic and PCOS adolescents, pulsatile LH release was determined without (baseline: B) and under constant testosterone (T) infusions: 0.75 (T 0.75) and 2.5 (T2.5) mg/12 h iv to 8 control adolescents (C) and 7 PCOS of similar chronological and gynecological age and normal BMI. C girls and 3 oligomenorrheic PCOS were studied at early follicular phase of 3 consecutive menstrual cycles. 4/7 PCOS in amenorrhea were studied monthly in three consecutive months. 20-min blood sampling for LH (IFMA) and T (RIA) measurements. was drowned during nocturnal 12 h at B , T 0.75 and T 2.5. LH characteristics were analyzed by Cluster program. Results: At B, T levels were significantly higher in PCOS than C (71±11 vs 40±7 ng/dl, p<0.01) but similar T serum levels were found in both groups under infusion. Analysis of LH secretory pulses in C adolescents on T 0.75 compared with B studies showed mean LH (4.5±1.0 vs 3.4±0.4 mUI/mL), pulse height (6.6±1.6 vs 4.9±0.4 mUI/mL) and nadir levels (2.9±0.8 vs 2.3±0.3 mUI/), all significantly higher(p<0.05). In C girls T 2.5 infusion produced a significantly suppressive effect on mean LH (2.3±0.3 vs B:3.4±0.4,mUI/mL, p<0.01), LH frequency (0.25±0.08 vs B:0.38±0.03 pulses/h, p<0.05) and LH nadir (1.3±0.3 mUI/mL vs B:2.9±0.8, p<0.01). PCOS did not show significant changes on LH secretory characteristics under both T infusions. Conclusion: Compared to normal adolescents, PCOS have substantially different responses to acute effects of T suggesting that an abnormal androgen negative feedback could be involved in this syndrome.