Neurodevelopmental outcomes are normal in congenital hypothyroid children diagnosed early and treated aggressively over the first three years

Despite marked improvements in developmental outcome with newborn screening and early levothyroxine replacement most follow up studies of congenital hypothyroidism (CH) show a persistent mild deficit in total IQ. It has been considered that these deficits in neurocognitive function occur in utero and thus even early therapy cannot completely normalise development. Alternatively the deficits could be caused by delayed diagnosis and inadequate early treatment. In Auckland, early diagnosis occurs via our newborn screening programme along with an aggressive high dose treatment paradigm following referral to the endocrine service. Thus we hypothesised that early diagnosis and aggressive therapy with close monitoring would result in normal neurocognitive outcomes.