Overnight growth hormone (GH) concentrations are supressed by testosterone (T) infusion in eumenorrheic and polycystic ovary syndrome (PCOS) adolescents.

ROPELATO MG; GARCIA RUDAZ MC; ESCOBAR ME; VELDHUIS JD; BARONTINI M

New York, N.Y., USA

Congreso; LWPES/ESPE 8TH JOINT MEETING; 2009

LWPES/ESPE , APEG, APPES, JSPE and SLEP

Chronic exposure to gonadal steroids increases GH secretion. It has been demonstrated that lean PCOS patients have increased GH secretion. This study was aimed to explore acute effects of T on the characteristics of overnight GH profile in eumenorrheic and PCOS adolescents with normal BMI. Seven non obese PCOS adolescents and 8 matched controls (C) were studied in the early follicular phase of 3 consecutive menstrual cycles or in 3 consecutive months. Overnight GH profiles (1900 to 0700 h) were determined during saline (B) and constant testosterone (T) infusions, low dose (T-LD): 0.75 and high dose (T-HD): 2.5 mg/12 h iv. Blood samples were withdrawn every 20 minutes. GH (ICMA) and T (ECLIA) were determined during all 3 infusions. Pulsatile GH characteristics were analyzed by Cluster program. Results: On T-LD, T levels increased 2-3 folds from B in control group (1.4±0.25 to 4.1±0.46 nmol/L) and in PCOS (from 2.4±0.30 to 4.6±0.54 nmol/L), whereas on T-HD values rose to 8.5 ± 0.96 and to 10.4±0.67 nmol/L in C and in PCOS, respectively. None of the characteristics of GH release was modified by T-LD infusion in either C or PCOS. However, T-HD blunted mean GH concentrations (Control B: 2.0±0.41 vs T-HD: 1.4±0.26 ìg/L; PCOS: 2.7±0.54 vs 1.5±0.28 ìg/L), maximum GH peak height (Control B: 6.7±1.4 vs T-HD: 4.1±0.76 ìg/L; PCOS: 8.4±1.5 vs 5.2±0.81 ìg/L), and increment peak amplitude (Control B: 6.4±1.4 vs T-HD: 3.9±0.75 ìg/L; PCOS: 8.1±1.4 vs 5.0±0.80 ìg/L) (all parameters p<0.05 vs B). GH frequency did not change. Conclusions: Similar responses to acute T infusion in both groups suggest that the effect of T in GH system is maintained in PCOS. The selective decrease in GH pulse amplitude by T-HD in both groups of adolescents may reflect inhibition by nonestrogenic metabolites of T.