Dihydrotestosterone treatment in adolescents with delayed puberty: does it explain insulin resistance of puberty?

Puberty is characterized by temporary insulin resistance, which subsides with the completion of pubertal development. This insulin resistance is manifested by lower rates of insulin-stimulated glucose metabolism and compensatory hyperinsulinemia in pubertal compared with prepubertal children. Whether or not pubertal insulin resistance is the result of sex steroids or GH or a combination of both has been investigated in our laboratory. Previously, we demonstrated that T treatment in adolescents with delayed puberty was not associated with the deterioration of insulin action. The present investigation evaluated the effects of 4 months of dihydrotestosterone administration (50 mg im every 2 wk) on body composition, glucose, fat, and protein metabolism, and insulin sensitivity. Ten adolescents with delayed puberty were evaluated before and after 4 months of DHT administration. Body composition was assessed by dual energy x-ray absorptiometry. Insulin-stimulated glucose metabolism was measured during a 3-h hyperinsulinemic (40 mU/m(2).min)-euglycemic clamp procedure. Lipolysis and proteolysis were evaluated by stable isotopes of [(2)H(5)]glycerol and [1-(13)C]leucine. After 4 months of dihydrotestosterone treatment, height, weight, and fat free mass increased and percentage of body fat decreased. IGF-I and nocturnal GH levels did not change. There was no significant change in insulin-stimulated glucose metabolism (57.2 +/- 3.9 vs. 58.3 +/- 3.9 micromol/kg.min). Total body proteolysis and lipolysis did not change. In summary, based on the present and past studies, we conclude that during puberty insulin resistance/hyperinsulinemia is not attributable to gonadal sex steroids in boys.

Glucose intolerance in obese adolescents with polycystic ovary syndrome: roles of insulin resistance and beta-cell dysfunction and risk of cardiovascular disease.

The roles of insulin resistance and insulin secretion in the pathogenesis of glucose intolerance in polycystic ovary syndrome (PCOS) were evaluated in 11 adolescents with impaired glucose tolerance (IGT) and 10 with normal glucose tolerance (NGT). Hepatic glucose production and insulin-stimulated glucose disposal were measured using [6,6-(2)H(2)]glucose and a 3-h hyperinsulinemic (80 mu/m(2).min)-euglycemic clamp. First and second phase insulin secretions were evaluated during a hyperglycemic clamp. Automated blood pressure measurements were made to assess the nocturnal change in blood pressure. Hepatic glucose production was significantly higher in IGT vs. NGT. Insulin-stimulated glucose disposal was not different between the two groups. The first phase insulin level was lower in IGT (207.9 +/- 21.0 vs. 357.0 +/- 62.9 muu/mL; P = 0.025; 1247 +/- 126 vs. 2142 +/- 377 pmol/L) without a difference in second phase insulin. The glucose disposition index (product of insulin sensitivity x first phase insulin) was lower in IGT vs. NGT (278 +/- 40 vs. 567 +/- 119 mg/kg.min; P = 0.023; 1546 +/- 223 vs. 3249 +/- 663 micromol/kg.min). The glucose disposition index correlated inversely with OGTT glucose concentrations at 30, 60, and 120 min. Adolescents with PCOS-IGT lacked the normal nocturnal decline in blood pressure. We conclude that in obese adolescents with PCOS, glucose intolerance is associated with 1) decreased first phase insulin secretion, 2) decreased glucose disposition index, and 3) increased hepatic glucose production. These metabolic abnormalities are precursors of type 2 diabetes and are present early in the course of PCOS. Furthermore, the absence of nocturnal dipping in blood pressure may herald the early expression of cardiovascular disease risk in these adolescents.

Early metabolic abnormalities in adolescent girls with polycystic ovarian syndrome.

OBJECTIVE: To investigate insulin sensitivity and secretion in young adolescent girls with childhood onset polycystic ovarian syndrome (PCOS) and to identify the early metabolic derangement(s). STUDY DESIGN: Twelve obese girls with PCOS (age 12.0+/-0.7 years) were compared with 10 obese nonhyperandrogenic girls (control group). The groups were matched for age, percent body fat, and abdominal fat. All subjects underwent a 3-hour hyperinsulinemic (80 mu/m(2)/min)-euglycemic clamp to determine in vivo insulin sensitivity and a 2-hour hyperglycemic clamp (225 mg/dL) to determine insulin secretion. Fasting hepatic glucose production was determined with the use of [6,6-(2)H(2)]glucose. RESULTS: Fasting glucose and hepatic glucose production were comparable between the 2 groups, but fasting insulin was 2-fold higher in the PCOS group. The fasting glucose to insulin ratio was lower in the PCOS group versus the control group (1.9+/- 0.3 vs 3.1+/-0.3, P =.02). During the hyperinsulinemic-euglycemic clamp, insulin sensitivity was lower in the PCOS group (1.4+/-0.2 vs 2.7+/-0.3 mg/kg/min per microu/mL, P =.002). During the hyperglycemic clamp, insulin secretion was significantly higher in the PCOS group. Insulin sensitivity correlated negatively with fasting insulin (r = -0.71, P =.0002) and positively with the fasting glucose to insulin ratio (r = 0.79, P<.0001). CONCLUSION: Adolescent girls with PCOS have profound metabolic derangements detected early in the course of the syndrome, including (1) approximately 50% reduction in peripheral tissue insulin sensitivity, (2) evidence of hepatic insulin resistance, and (3) compensatory hyperinsulinemia. These observations may predict an increased risk of type 2 diabetes mellitus in adolescents with PCOS.

Determination of body composition in African-American children: validation of bioelectrical impedence with dual energy X-ray absorptiometry.

Body compositional differences between Black and White adults are well-known. It has become increasingly apparent that these racial variations may begin in childhood. Previously, our group validated tetrapolar bioelectrical impedance (BIA) measurements against H2(18O) dilution method to develop prediction formulas of fat free mass (FFM) in healthy White-American children: FFM = 0.524 Ht2/R + 0.415 Wt 0.32. In the present study we used BIA to establish a FFM prediction equation for forty African-American children (19 males and 21 females). Of the females, six were diagnosed with polycystic ovary syndrome (PCOS) and were obese. FFM was determined by dual energy X-ray absorptiometry (DEXA). Impedence measurements by BIA showed a strong correlation with FFM determined by DEXA. In healthy Black children, FFM = 0.84 Ht2/R + 1.10 with a standard error of estimate (SEE) of 1.47 kg (R2 = 0.97). In Black females with PCOS, FFM = 0.62 Ht2/R + 0.21 Wt - 1.94 with a SEE of 1.43 kg (R2 = 0.99). The observed differences in the prediction equations of FFM between White-American and African-American children underline the importance of using race-specific formulas in evaluating body composition. With the overall increase in rates of childhood obesity and more so in the Black race, BIA is an easy and useful tool for the assessment and follow up of body compositional changes with lifestyle interventions.