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Does early identification of central congenital hypothyroidism result in improved outcomes?

The case for detecting primary congenital hypothyroidism (CH) by measuring thyroidstimulating hormone (TSH) on dried blood spots (DBSs) was made in the late 1970s and is now established practice in newborn screening (NBS) programs in developed countries (1). Detection of TSH is sufficient for the detection of infants at risk of primary CH, but screening for central CH requires both thyroxine (T4) and TSH measurement. The comprehensive screening protocol employed in the Netherlands since 1995 involves primary T4 testing and supplementary or “reflex” TSH testing in patients with the lowest quintile of T4 concentrations, along with thyroxine-binding globulin (TBG) measurement for the lowest 5% of T4 concentrations and calculation of the T4/TBG ratio (2). However, most countries offer a TSH-only screening service, particularly in the light of more sensitive TSH cut-offs. In the United States, a recent review showed that TSH-only screening was used in 22 of 51 screening jurisdictions, initial T4 measurement with reflex TSH screening if T4 <10th centile in 22, and combined T4 and TSH measurement in all newborn DBS in 9 jurisdictions (3).