Fasting glucose insulin ratio: A useful measure of insulin resistance in girls with premature adrenarche

The purpose of this study was to determine whether the fasting glucose/insu lin ratio is a useful screening test for insulin resistance in prepubertal girls with premature adrenarche. The glucose/insulin ratio was compared wit h the insulin sensitivity index calculated from the frequently sampled iv g lucose tolerance test with tolbutamide using the minimal model computer pro gram. Thirty-three prepubertal girls (22 Caribbean Hispanic and 11 African American; mean age, 6.8 yr; bone age, 8 yr) were studied. All underwent a 6 0-min ACTH stimulation test. The fasting glucose/insulin ratio was also com pared with IGF-binding protein-1 and ACTH-stimulated androgen levels. Insul in sensitivity correlated significantly with the glucose/insulin ratio (0.7 6; P < 0.001), fasting insulin (0.75; P < 0.001), and IGF-binding protein-1 (0.59; P < 0.005). Stepwise regression analysis with the insulin sensitivi ty index as the dependent variable showed that the fasting glucose/insulin ratio was significantly predictive of the insulin sensitivity index (P < 0. 002). When viewed as a screening test, setting a value of the fasting gluco se/ insulin ratio of less than 7 as abnormal and of less than 5.7 x 10(-4) min/muU.ml for the insulin sensitivity index as evidence of insulin resista nce (normal prepubertal insulin sensitivity index, >5.7 x 10(-4) min/muU.ml ), the sensitivity of the fasting glucose/insulin ratio was 87%, and the sp ecificity was 89%. Furthermore, those girls with a low glucose/insulin rati o (<7) had higher body mass index, fasting insulin, free T, and ACTH-stimul ated 17-hydroxypregnenolone and lower fasting IGF-binding protein-1 and SHB G than those girls with a glucose/insulin ratio greater than 7. The fasting glucose/insulin ratio is a useful screening test for insulin resistance in prepubertal Caribbean Hispanic and African American girls with premature a drenarche.