The natural history of congenital hypothyroidism with delayed TSH elevation in neonatal intensive care newborns

Objective To assess the clinical and neurological outcomes in newborns with primary congenital hypothyroidism presented with delayed TSH elevation (dTSH), and to define parameters that may predict the evolution of transient vs. permanent hypothyroidism in these newborns. Design and patients An observational study was performed of a cohort of 113 children with a history of dTSH. Measurements Birth parameters, thyroid screening results, thyroid gland imaging, levothyroxine dose and neurological outcome were compared between newborns with spontaneous recovery and children with a final diagnosis of either transient or permanent hypothyroidism. Results Of the children with a history of dTSH, 93% demonstrated recovery, either spontaneously or following levothyroxine treatment (transient hypothyroidism). Newborns with spontaneous recovery demonstrated milder thyroid dysfunction at the newborn screening compared to those who started levothyroxine treatment. Levothyroxine dose was lower in children with transient vs. permanent hypothyroidism only during the first 6 months of life; otherwise, these groups were similar in birth parameters, thyroid screening results and gland images. Seventeen out of 61 children (28%) that underwent neurological assessment demonstrated a developmental delay. Duration of treatment was highly variable in children with transient hypothyroidism. Conclusions Thyroid dysfunction is transient in most cases of dTSH. No reliable parameters can predict a priori transient vs. permanent hypothyroidism.