ESPE Abstracts

Background: Mild TSH elevations are frequently observed in obese patients, in the absence of any detectable thyroid disease.

Aims and objective: To evaluate possible causes for the raised TSH levels and to verify possible biochemical and clinical consequences of this condition.

Methods: We evaluated 779 (325 males/454 females) obese children, chronological age 14.38±2.56 (range 5.25 to 18.50), height SDS 0.27±1.04 (range −3.49 to 4.35), BMI–SDS 2.94±0.59 (range 1.6 to 4.62). After an overnight fast, they were admitted to the ward, for auxological evaluation, assessment of body composition by bioelectrical impedance analysis and energy expenditure by indirect calorimetry. A blood sample was obtained for the determination of thyroid function (fT₄, TSH, TPOAbs, and TGAbs), inflammation markers (total WBC and the subtypes, C-reactive protein), metabolic parameters (AST, ALT and yGT, glycaemia, insulin, total-, HDL- and LDL-cholesterol, triglycerides). An OGTT was performed for the assessment of glucose tolerance and for the calculation of the disposition index (ODI). The patients were then subdivided in two groups according to a TSH value above (group 1) or below (group 2) 4.5 mU/l.

Results: Group 1 showed significantly higher values of AST (24.8±12.2 S.D. vs 22.5±9.6 S.D.; P<0.05), total cholesterol (170.3±28.7 vs 163.3±32.9; P<0.05), azotemia (28.9±5.3 vs 27.1±5.4; P=0) and alkaline phosphatase (168.6±89.7 vs 149.3±87.2; P<0.05). Multiple regression analysis showed that TSH serum levels was negatively affected by age (P<0.05) and positively by BMI–SDS (P<0.001) and total lymphocytes count (P<0.01). Because of the cardiovascular implications we also checked the determinants of cholesterol serum levels: AST (P<0.01) and TSH (P<0.05) were involved; however the model explained only 2% of the probability.

Discussion: Fat excess and the consequent inflammatory status seem to be the main determinants of TSH elevation, probably through a negative influence on inflammatory cytokines on the TSH receptor. The raised TSH is a poor predictor of serum cholesterol levels.