Gender, age, puberty, and BMI related changes of TSH and thyroid hormones in schoolchildren living in a long-standing iodine replete area

Abstract

The aim of the work was to assess thyroid function in children and adolescents in an iodine replete area and to explore possible effects of age, gender, puberty, and adiposity. Thyrotropin (TSH), total triiodothyronine (T, total thyroxine (T, free thyroxine (FT, and the TTratio were determined for 440 schoolchildren (200 boys and 240 girls), aged 518 years, living in an iodine replete region. Body Mass Index (BMI), BMI standard deviation score (BMI-SDS), and Body Surface Area (BSA) were calculated. In girls there was a negative correlation of TSH, T and FTvalues with age. In boys there was a negative correlation only of Tvalues with age. Girls had lower TSH, T and Tvalues, whereas boys had only lower Tvalues at puberty compared to the prepubertal stage. Girls had lower TSH values than boys (p<0.03) only at puberty. BMI-SDS in boys and girls were 0.21 and 0.03, respectively. BMI-SDS was not related to TSH, T or Tin either gender, whereas it was negatively related to TTratio in boys and to FTin girls. We conclude that estrogens may exert a suppressive effect on the pituitary-thyroid axis after puberty. TSH values are not correlated with BMI-SDS, whereas TTratio in boys and FTin girls are negatively correlated with BMI-SDS. © Georg Thieme Verlag KG Stuttgart New York