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Higher BMI may increase free T3 levels in children
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Free triiodothyronine levels are causally increased by higher BMI and fat mass in children, according to recent study findings.
“Our observational analyses clearly show that [free] T3 and [free thyroxine] have opposing strong correlations with body composition in childhood; with [free] T3 being positively associated and [free] T4 negatively associated with fat mass and BMI,” the researchers wrote.
Peter N. Taylor
Peter N. Taylor, BSc, MBChB, MSc, of the Thyroid Research Group of the Institute of Molecular and Experimental Medicine at Cardiff University School of Medicine in the United Kingdom, and colleagues evaluated data from the Avon Longitudinal Study of Parents and Children, a population-based cohort, on 3,014 children to determine whether childhood adiposity influences free T3 levels. Thyroid function was measured at age 7 years and DXA scans were done at 9.9 years and 15.5 years. Genetic data also were available.
A positive association was found between BMI and free T3 at age 7 years, whereas a negative association was found between BMI and free T4; after adjustment for age, sex and early life environment, the differences persisted.
At age 7 years, a genetically higher BMI of 1.89 kg/m2 was linked to a 0.22 pmol/L increase in free T3 (P = .004). No association was found between a genetically higher BMI and free T4 (P = .96).
“Our analysis has indicated that BMI and adiposity causally increase [free] T3 levels in children,” the researchers wrote. “More research is required to identify the causal mechanisms for this and the consequences of childhood obesity on this relationship.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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