Positive correlation of thyroid hormones and serum copper in children with congenital hypothyroidism

Thyroid hormones are of central relevance for growth and development. However, the underlying molecular mechanisms are still not fully understood. Recent studies in humans and mice have demonstrated that serum levels of selenium (Se) and copper (Cu) are positively affected by thyroid hormones. Given the importance of these trace elements for many biochemical processes, we tested whether this interaction is found in children at risk for hypothyroidism, potentially providing a novel factor contributing to the disturbed development observed in congenital hypothyroidism (CH). We conducted a cross-sectional analysis of 84 children diagnosed with CH displaying a wide range of thyroid hormone concentrations. Serum Se and Cu concentrations were measured by total reflection X-ray fluorescence. Data for thyrotropin (TSH) were available in all, thyroxine (T4) and free thyroxine (fT4) in the majority and triiodothyronine (T3) in 29 of the children. Spearman rank analyzes were performed. Cu and thyroid hormones showed a strong positive correlation (Cu/T4, rho=0.5241, P=0.0003; Cu/T3, rho=0.6003, P=0.0006). Unlike in adults, no associations were found between Se and any of the thyroid hormones. Our data highlight that serum Cu and thyroid hormones are strongly associated already in early postnatal life. Severely hypothyroid children are thus at risk of developing a Cu deficiency if not adequately nourished or supplemented. This finding needs to be verified in larger groups of children in order not to miss an easily-avoidable risk factor for poor development.