Growth hormone, insulin-like growth factor-I axis, and insulin secretion in hyperandrogenic adolescents

Objective To assess GH and insulin-like growth factor I (IGF-I) axis variability in hyperandrogenic adolescents with different sources of androgen excess and their relationship with insulin resistance. Design Baseline IGF-I, insulin-like growth factor binding protein-1 (IGFBP-1), IGFBP-3, GH response to the exercise-propranolol test, and insulin responses to a standard oral glucose tolerance test were compared among patients with functional ovarian hyperandrogenism, hyperandrogenic nonfunctional ovarian hyperandrogenism patients, and age-matched controls. Setting Outpatient clinic in a medical center. Patients Twenty-one adolescents with ovarian (group A) and 17 with nonovarian (group B) hyperandrogenism, and 20 controls. Results Serum IGF-I and poststimulated GH levels were similar among groups, whereas serum IGFBP-3 levels were significantly lower in group A than in controls. Mean serum insulin levels were significantly higher in patients than in controls, whereas 24% of patients had abnormal insulin responses to glucose and/or insulin sensitivity indexes. Serum IGFBP-3 levels correlated negatively with the free androgen index (free androgen index=T/sex hormone-binding globulin [SHBG]×100), whereas mean serum insulin levels correlated positively with the free androgen index and negatively with SHBG levels in all subjects. Conclusions Hyperinsulinemia is common in hyperandrogenic adolescents and correlates with the degree of hyperandrogenism and not with the androgen source. Hyperinsulinemia and decreased IGFBP-3 levels may enhance IGF-I bioavailability, which in turn may both decrease SHBG levels and increase androgen production.