Zeitschrift für Neonatalbiologie

Abstrakt

Neonatal dysregulation of the pituitary-thyroid axis with combined thyroid hormone and thyrotropin resistance in infants with trisomy 21 and maternal subclinical hypothyroidism

Sze May Ng, Astha Soni and Mohammed Didi

Trisomy 21 is often associated with thyroid problems. Although autoimmune hypothyroidism is the most common thyroid problem in trisomy 21, dysregulation of the pituitary-thyroid axis is also known to occur in infants with this chromosomal disorder. This results in elevated thyrotropin (TSH) levels in the absence of autoimmunity and structurally normal thyroid. The mechanism of this phenomenon is not clearly understood and it is possible that this is due to a genomic imbalance due to the trisomy of chromosome 21. Some authors have suggested that thyroid hormone resistance (RTH) may be a contributing factor to this. However, the genes encoding the TSH receptor and the two proteins known to be involved in TSH resistance are normal in patients with trisomy 21. In newborns, transient hyperthyrotropinemia is associated with a positive maternal thyroid peroxidase antibody (TPO). We describe the case of a newborn with trisomy 21 identified during a screening for congenital hypothyroidism in newborns. The newborn had a high TSH level and elevated plasma free T4 (FT4) with clinical signs and symptoms consistent with congenital hypothyroidism. We discuss the management of this case and possible mechanisms contributing to this unusual clinical picture.