When should we be conducting thyroid function tests in newborns and young infants?

An audit of local practice was undertaken as regards requests for thyroid function tests (TFT) in children aged between birth and 3 months at two local hospitals in South West England between 2005 and 2008. A total of 406 tests were performed (2.6 tests per week) over a 2-year period at a teaching hospital (70 tests per 1000 live births yearly), with 233 tests (1.5 tests per week) performed over a 3-year period at a local district hospital (39 tests per 1000 live births yearly). The highest proportion of all the tests was performed as routine investigation of prolonged neonatal jaundice (64% and 55%, respectively). Other common indications were maternal thyroid disorders (5.4% vs 4.7%) and suspected neonatal thyroid disorders (3% vs 9%). There was no confirmed diagnosis of infantile thyroid disease. Available evidence and this audit suggest that too many thyroid function tests are unnecessarily performed in young infants.