ESPE Abstracts

Background: The interrelationships between body weight and thyroid status are complex. Serum TSH is typically increased in obese compared with lean individuals. Several mechanisms leading to hyperthyrotropinemia have been hypothesized.

Objective and hypotheses: To compare thyroid function and autoimmunity in normal, overweight and obese healthy children and adolescents in our population. To analyse any metabolic risk factor related to hyperthyrotropinemia.

Method: Cross-sectional epidemiological study. By a multistage probability sampling 1317 children and adolescents aged between 2 and 16 were selected. Physical and laboratory examination were performed including weight, height, waist circumference, neck palpation, blood pressure, glucose, insulin, triglycerides, HDL-cholesterol, urinary iodine, free thyroxine (T₄), TSH, antiperoxidase, and antithyroglobulin antibodies. Thyroid autoimmunity was diagnosed when any antibody was positive. BMI was calculated and obesity and overweight were diagnosed using the threshold proposed by the International Obesity Task Force for children and adolescents. χ² and ANOVA tests were used.

Results: TSH levels (mU/l) were significantly higher in the obese (3.12 (2.44)) (mean (S.D.)) than in the overweight (2.79 (1.51)) and normal children and adolescents (2.73 (1.30)) (P=0.02), while T₄ and urinary iodine levels did not differ. Prevalence of thyroid autoimmunity was lower in normal (2.9%) than in overweight (6.3%) and obese individuals (5.6%) (p=0.02). When excluding subjects with autoimmunity, TSH levels were less different comparing the three groups: obese 2.98 (1.17), overweight 2.73 (1.17), and normal weight 2.72 (1.19) (P=0.09). Hyperthyrotropinemia in obese and overweight children and adolescents was not related to any variable.

Conclusion: TSH levels are significantly higher in obese than in overweight and normal children and adolescents. Significance is statistical but not clinical. Hyperthyrotropinemia in obese and overweight children and adolescents is not related to any cardiovascular risk factor.