title: Association between thyrotropin levels and insulin sensitivity in euthyroid obese adolescents.
abstract: BACKGROUND
  Thyrotropin (TSH) levels display a positive association with body mass index (BMI), and the prevalence of isolated hyperthyrotropinemia is higher in obese adolescents compared to their normal weight controls. However, the metabolic significance of the higher TSH in obese adolescents is less clear. The objective of this study was to determine the relationship between TSH concentrations and insulin sensitivity, lipids, and adipokines in euthyroid, non-diabetic, obese adolescents.
  
  
  METHODS
  Thirty-six euthyroid, non-diabetic, obese adolescents between the ages of 12 and 18 years underwent a 75 g oral glucose tolerance test. Insulin sensitivity (Si) and pancreatic β-cell function as assessed by disposition index (DI) were measured using the oral glucose minimal model approach. Cholesterol (total, low-density lipoprotein [LDL-C], and high-density lipoprotein [HDL-C]), triglycerides (TG), interleukin-6 (IL-6), total and high molecular weight (HMW) adiponectin, and retinol binding protein-4 (RBP4) were also determined. Associations between measures of thyroid function and Si, DI, lipids, and adipokines were computed using Pearson's correlation coefficient and multiple regression analysis.
  
  
  RESULTS
  The mean age of the subjects was 14.3±1.88 years, and the mean BMI was 32.5±4.65 kg/m2; 97% were non-Hispanic white and 47% were male. The mean TSH was 2.7±1.2 mIU/L. Increasing serum TSH was correlated with decreasing Si (log Si) in the entire cohort (p=0.03), but this relationship persisted only in males (p=0.02). The correlation between TSH and Si in males remained significant after adjusting for BMI (p=0.02). There was no correlation between TSH and pancreatic β-cell function as assessed by DI (p=0.48). TSH correlated positively with LDL-C (p=0.04) and IL-6 (p=0.03), but these associations vanished or weakened after adjusting for BMI (LDL-C p-value=0.44; IL-6 p-value=0.07).
  
  
  CONCLUSIONS
  This study suggests a sex-specific association between TSH and insulin sensitivity in euthyroid, non-diabetic, obese adolescent males. Prospective studies are warranted to explore further this sexual dimorphism in the relationship between thyroid function and insulin sensitivity and to determine if obese adolescents with insulin resistance receiving thyroid supplements for hypothyroidism would benefit from targeting TSH levels in the lower half of normal range.
authors.affiliation: 1 Division of Pediatric Endocrinology, Department of Pediatric and Adolescent Medicine, Mayo Clinic , Rochester, Minnesota.
authors.forename: Asma
authors.initials: A
authors.lastname: Javed
authors.forename: P Babu
authors.initials: PB
authors.lastname: Balagopal
authors.forename: Adrian
authors.initials: A
authors.lastname: Vella
authors.forename: Philip R
authors.initials: PR
authors.lastname: Fischer
authors.forename: Francesca
authors.initials: F
authors.lastname: Piccinini
authors.forename: Chiara
authors.initials: C
authors.lastname: Dalla Man
authors.forename: Claudio
authors.initials: C
authors.lastname: Cobelli
authors.forename: Paula D
authors.initials: PD
authors.lastname: Giesler
authors.forename: Jeanette M
authors.initials: JM
authors.lastname: Laugen
authors.forename: Seema
authors.initials: S
authors.lastname: Kumar
mesh_terms: D000293:Adolescent; D001786:Blood Glucose / Q000378:metabolism*; D015992:Body Mass Index; D002648:Child; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D008055:Lipids / Q000097:blood; D008297:Male; D009765:Obesity / Q000097:blood* / Q000503:physiopathology; D011446:Prospective Studies; D013961:Thyroid Gland / Q000503:physiopathology*; D013972:Thyrotropin / Q000097:blood*
chemical_list: D001786:Blood Glucose; D007328:Insulin; D008055:Lipids; D013972:Thyrotropin