Infants of hypothyroid mothers- are postnatal Thyroid Function Tests necessary? A Retrospective Study in a Regional Hospital.

Congenital hypothyroidism is a preventable cause of intellectual disability. The aim of this study was to establish whether adding an additional thyroid function check between days of life 10-14 in infants born to mothers with known hypothyroidism identified any additional cases of congenital hypothyroidism requiring treatment that were not detected by the national newborn bloodspot screening programme. Babies who had Thyroid Function Tests (TFTs) measured at 10-14 days of age were identified using the Paediatric Ward attenders log from the years 2012-2014. Data were collected on patients' TFTs and their mothers' Anti-Thyroid Peroxidase (Anti-TPO) antibody levels. Of the 121 patients included, none were found to have a significantly raised TSH requiring treatment. 40 infants had repeat TFTs performed. None of the 121 infants had a significantly raised TSH, which required treatment with thyroxine. Congenital hypothyroidism is already being screened for as part of the National Newborn Screening Programme. The findings of our study have led us to recommend stopping current practice of routinely checking TFTs on day 10-14 of life in infants of hypothyroid mothers.