title: Thyroid function tests in obese prepubertal children: correlations with insulin sensitivity and body fat distribution.
abstract: OBJECTIVE
  Elevated thyroid-stimulating hormone (TSH) concentrations in association with normal/slightly elevated free triiodothyronine (fT(3)) and/or free thyroxine (fT(4)) have been consistently found in obese children. To examine relationships between adiposity, insulin sensitivity, and TSH, fT(3) and fT(4).
  
  
  METHODS
  240 overweight/obese prepubertal children were studied. Fasting TSH, fT(3), fT(4), glucose, insulin, C-peptide, lipids, leptin and adiponectin were evaluated. Insulin sensitivity and resistance were estimated [quantitative insulin check index (QUICKI), insulin sensitivity index (ISI), and hepatic insulin resistance index]. Body fat was measured by dual-energy X-ray absorptiometry. The central obesity index was calculated as the ratio of fat tissue in the trunk region to fat tissue in the leg region.
  
  
  RESULTS
  The multiple regression analysis with age, gender and measures of fatness as covariates showed that QUICKI was the only significant negative predictor of TSH and central obesity index the strongest positive predictor of fT(3), in association with either age or hepatic insulin resistance index, and that the only positive determinant of fT(4) was hepatic insulin resistance index.
  
  
  CONCLUSIONS
  Reduced insulin sensitivity is associated with augmented TSH and fT(4), while progressive central fat accumulation is strictly related to a parallel increase in fT(3) levels, independently from total body fat. Further studies are needed to understand mechanisms linking thyroid function to insulin sensitivity and body composition in obese children.
authors: Endocrinology and Diabetes Unit, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy. cbrufani@libero.it
authors: Claudia
authors: C
authors: Brufani
authors: Melania
authors: M
authors: Manco
authors: Valerio
authors: V
authors: Nobili
authors: Danilo
authors: D
authors: Fintini
authors: Fabrizio
authors: F
authors: Barbetti
authors: Marco
authors: M
authors: Cappa
mesh_terms: D052242:Adiponectin / Q000097:blood; D050154:Adiposity; D001786:Blood Glucose / Q000378:metabolism; D002096:C-Peptide / Q000097:blood; D002648:Child; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D020738:Leptin / Q000097:blood; D008055:Lipids / Q000097:blood; D008297:Male; D009765:Obesity / Q000097:blood*; D013960:Thyroid Function Tests; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*
chemical_list: D052242:Adiponectin; D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D020738:Leptin; D008055:Lipids; D014284:Triiodothyronine; D013974:Thyroxine