title: Reduction of plasma insulin levels does not restore integrated concentration of growth hormone to normal in obese children.
abstract: Obesity in childhood is characterized by subnormal integrated concentrations of growth hormone (IC-GH) and elevated integrated concentrations of insulin (IC-I). We tested whether a reduction of IC-I induced by a low calorie diet would lead to a rise of IC-GH into the normal range for age. Six obese children (body mass index (BMI) 39.1 +/- 9.2 kg/m2) underwent integrated concentration (IC) studies by continuous withdrawal before and again 5-8 weeks after being on a low calorie diet. In response to the diet BMI was lower 34.7 +/- 9.4 kg/m2 (P less than 0.003), and IC-I was considerably reduced, 479 +/- 255 pM initially vs. 109 +/- 109 pM on the diet, P less than 0.0008. IC-GH increased modestly from 1.6 +/- 0.6 micrograms/l initially to 2.4 +/- 0.6 micrograms/l, P less than 0.01 on the diet. None of the patients had repeat IC-GH levels which were above the lower limit of normal for lean children of normal stature (3.2 micrograms/l). Single sample insulin-like growth factor 1 (IGF-1) levels were unchanged: 40.9 +/- 23.1 nM initially vs. 49.7 +/- 25.7 nM (314.6 +/- 197.7 vs. 382.5 +/- 217.0 ng/ml, n.s.). Thus reduction of high insulin concentrations during 5-8 weeks of a low calorie diet has only a small effect on IC-GH in obese children. Factors other than circulating insulin levels are likely to play the major role in mediating the reduced levels of GH observed in obesity.
authors.affiliation: Division of Pediatric Endocrinology, University of Maryland School of Medicine, Baltimore 21201.
authors.forename: S A
authors.initials: SA
authors.lastname: Chalew
authors.forename: R A
authors.initials: RA
authors.lastname: Lozano
authors.forename: K M
authors.initials: KM
authors.lastname: Armour
authors.forename: A A
authors.initials: AA
authors.lastname: Kowarski
mesh_terms: D000293:Adolescent; D015992:Body Mass Index; D001835:Body Weight; D002648:Child; D002675:Child, Preschool; D004038:Diet, Reducing; D002149:Energy Intake; D005260:Female; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D007328:Insulin / Q000097:blood*; D007657:Ketone Bodies / Q000652:urine; D008297:Male; D009765:Obesity / Q000097:blood* / Q000178:diet therapy
chemical_list: D007328:Insulin; D007657:Ketone Bodies; D013006:Growth Hormone