Department of Pediatrics, Division of Pediatric Endocrinology, Albert Einstein College of Medicine/Children's Hospital,. Montefiore Medical Center, Bronx, New ...
0013-7227/01/$03.00/0 Printed in U.S.A.
The Journal of Clinical Endocrinology & Metabolism 86(10):4618 – 4621 Copyright © 2001 by The Endocrine Society
Fasting Glucose Insulin Ratio: A Useful Measure of Insulin Resistance in Girls with Premature Adrenarche PATRICIA VUGUIN, PAUL SAENGER,
AND
JOAN DIMARTINO-NARDI
Department of Pediatrics, Division of Pediatric Endocrinology, Albert Einstein College of Medicine/Children’s Hospital, Montefiore Medical Center, Bronx, New York 10467 The purpose of this study was to determine whether the fasting glucose/insulin ratio is a useful screening test for insulin resistance in prepubertal girls with premature adrenarche. The glucose/insulin ratio was compared with the insulin sensitivity index calculated from the frequently sampled iv glucose tolerance test with tolbutamide using the minimal model computer program. 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 60-min ACTH stimulation test. The fasting glucose/insulin ratio was also compared with IGFbinding protein-1 and ACTH-stimulated androgen levels. Insulin sensitivity correlated significantly with the glucose/insulin ratio (0.76; P < 0.001), fasting insulin (0.75; P < 0.001), and IGFbinding protein-1 (0.59; P < 0.005). Stepwise regression analysis with the insulin sensitivity index as the dependent variable showed that the fasting glucose/insulin ratio was significantly
T
HE TERM INSULIN resistance refers to an impaired biological response to either exogenous or endogenous insulin (1). The euglycemic insulin clamp and the frequently sampled iv glucose tolerance test (FSIVGTT) are the standard methods of assessing insulin sensitivity (SI) (2, 3). These tests are time, labor, and cost intensive and are not practical for large scale studies, screening, or routine assessment. It is well established that polycystic ovarian syndrome (PCOS) is frequently characterized by insulin resistance (4). Recently, Legro et al. (5) compared the fasting glucose/insulin (G:I) ratio to insulin sensitivity measured by the FSIVGTT in obese non-Hispanic white women with PCOS. The fasting G:I ratio was found to be a highly sensitive and specific measurement of insulin sensitivity. When viewed as a screening test for insulin resistance, a fasting G:I ratio of less than 4.5 in obese Caucasian women was considered abnormal, with 95% sensitivity and 84% specificity. We previously reported that approximately 50% of Caribbean Hispanic and African American prepubertal girls with premature adrenarche also have insulin resistance when measured by the FSIVGTT. Furthermore, the hyperandrogenism in these girls correlated inversely with their insulin sensitivity (6, 7). That is, the more insulin-resistant girls had the higher ACTH-stimulated androgen levels. In addition to insulin resistance, many girls with premature adrenarche have many of the clinical and laboratory features of Abbreviations: AS, Androstenedione; BMI, body mass index; DHEA, dehydroepiandroesterone; FSIVGTT, frequently sampled iv glucose tolerance test; G:I ratio, glucose/insulin ratio; IGFBP, IGF-binding protein; 17-OH Preg, 17-hydroxypregnenolone; 17-OH Prog, 17-hydroxyprogesterone; PCOS, polycystic ovarian syndrome; SI, insulin sensitivity.
predictive of the insulin sensitivity index (P < 0.002). When viewed as a screening test, setting a value of the fasting glucose/ insulin ratio of less than 7 as abnormal and of less than 5.7 ⴛ 10ⴚ4 min/U䡠ml for the insulin sensitivity index as evidence of insulin resistance (normal prepubertal insulin sensitivity index, >5.7 ⴛ 10ⴚ4 min/ U䡠ml), the sensitivity of the fasting glucose/insulin ratio was 87%, and the specificity was 89%. Furthermore, those girls with a low glucose/insulin ratio (
