Overweight And Obese Affects Thyroid Function And Structure In School-age Children And Adolescents

Objective: To investigate the effects of overweight and obese on thyroid function and structure in school-age children and adolescents.Methods: A cross-sectional survey with stratified cluster sampling was conducted in four districts in Bengbu city, Anhui province, 959 subjects aged 7-18 were recruited from subgroups of overwight, obese and nomal weight which were screened by body mass index (BMI). 781 of the subjects, included 327 obese, 242 overweight and 212 normal body weight, were brought into the study and futher accepted blood pressure, waist circumference and abdominal circumference measurement. Blood samples were collected in fasting status to test thyroid stimulating hormone (TSH), serum free triiodothyronine (FT3), free thyroxin (FT4), thyroid peroxidase antibodies (TPOAb) and thyroid ultrasound.Results: (1) FT3 and TSH were both positively correlated with BMI and waist circumference, while FT4 was negatively associated with them, even after adjustment for age and sex. Overweight and obesity significantly affected thyroid function for children through elevated TSH and FT3 and decreased FT4. (2) BMI and waist circumference (WC) were positively correlated with thyroid volume (rBMI=0.514, rWC =0.454, respectively) even after adjustment for age and sex. The positive rate of thyroid nodule was slightly higher in the obese and overweight cases than normal subjects. (3) Of all 569 overweight and obese children and adolescents, only 3 children showed detectable antithyroid antibodies and an ultrasound pattern suggestive of Hashimoto's thyroiditis (HT) (group A) and 6 showed detectable antithyroid antibodies with normal ultrasound finding (group B). A total of 74 subjects showed absent antithyroid antibodies with an ultrasound pattern suggestive of HT (group C), while 486 children and adolescents showed no thyroid antibodies with normal ultrasound finding (group D). TSH levels was higher in groups A and D compared with controls (P<0.05), whereas FT3 was higher in group C and D than in normal subjects (P<0.05).Conclusions: Our results suggest that thyroid function could be affected in obese and overweight children and adolescents. In additon, thyroid volume is increased and the detection rate of thyroid nodules is higher in obese and overweight than normal controls. Alterations of thyroid structure and function couldn't be completely explained by the presence of an autoimmune involvement. The impairment of hypothalamic-pituitary-thyroid axis and the low grade inflammation may be involved in the change of thyroid function and structure.