ESPE Abstracts

Studies in adults provide convincing evidence of seasonal fluctuations in thyroid hormone levels. However, the evidence in children and adolescents is less consistent, potentially due to unaddressed confounding and the use of statistical methods not well-suited to investigate this specific issue. Using the baseline data from KiGGS (German Health Interview and Examination Survey for Children and Adolescents), an analysis was conducted among 6,071 participants aged 6 to 17 years who were deemed healthy with respect to thyroid function (including normal thyroid levels, absence of thyroid autoantibodies, no known thyroid diseases or medication use, and normal urinary iodine levels) to investigate whether thyroid hormone levels (TSH, fT4, and fT3) standardized by age and sex exhibit seasonal variations. This analysis employed models specifically designed for time series analysis and complex underlying biological processes, including both a Cosinor model and a SARIMAX model. Utilizing these models and accounting for a wide range of covariates (e.g., BMI, puberty status, the time of blood sampling, and average monthly temperature), there is not consistent support to seasonal variations in thyroid hormone levels among children and adolescents. This conclusion was further supported by various sensitivity analyses. Unlike findings in adults, there is no clear evidence of seasonal changes in thyroid hormone levels in children and adolescents. It is possible that seasonal variations are obscured by other factors, particularly those associated with developmental processes in the hypothalamic-pituitary-thyroid axis, which may mask any seasonal effects.