Thyroid function and structure are affected in childhood obesity.

OBJECTIVE Alterations in thyroid function are reported in obesity, although no relevant data exist on the thyroid structure of these patients and the frequency of autoimmunity. The aim of our study was to evaluate the involvement of the thyroid gland in a large group of obese children. DESIGN This was a cross-sectional study. METHODS The study was conducted between March 2004 and December 2007 in 186 overweight and obese children. In all subjects, serum free T(3), free T(4), TSH, antithyroid antibodies, and a thyroid ultrasound were assessed. A total ot 40 healthy children matched for age and of normal weight for height served as controls. RESULTS A total of 23 children (12.4%) showed antithyroid antibodies and an ultrasound pattern suggestive of Hashimoto's thyroiditis (group A). Of them, 20 (10.8%) showed antithyroid antibodies and normal ultrasound (group B). A total of 70 subjects (37.6%) showed absent antithyroid antibodies and an ultrasound pattern suggestive of Hashimoto's thyroiditis (group C), and 73 children (39.2%) showed no thyroid antibodies with normal ultrasound (group D). TSH was higher in groups A and C compared with groups B and C, and controls (P < 0.05). Mean free T(4) was lower in group B (P < 0.05) than in controls, whereas free T(3) was higher in group C than in controls (P < 0.05). TSH and body mass index sd scores were significantly correlated in group C (P < 0.001), and TSH was also significantly associated with the degree of thyroid structure alterations (P < 0.05). CONCLUSION Obese children frequently show alterations of thyroid structure and function that are not completely explained by the presence of an autoimmune involvement.