Transient infantile hyperthyrotrophinaemia.

Sixteen cases of transient infantile hyperthyrotrophinaemia were followed up for two to seven years. Concentrations of serum triiodothyronine, thyroxine, and free thyroxine were maintained within the normal range in all cases. All but one child, who had a hearing disturbance, showed normal mental development with normal physical and skeletal maturation. Eleven children had normal concentrations of serum thyroid stimulating hormone and no signs or symptoms of thyroid dysfunction; in three children, diffuse small goitres developed and two further children showed relapse with slightly raised concentrations of thyroid stimulating hormone. It is concluded that 'transient infantile hyperthyrotrophinaemia' is a syndrome, which differs from typical transient neonatal hypothyroidism, and that careful follow up is necessary because some children show signs of mild pituitary-thyroid dysfunction in later childhood.