Neonatal Thyroid Disease

: Thyroid dysfunction that requires prompt diagnosis and treatment often becomes evident in the newborn period because of testing that is done as part of universal newborn screening. Primary congenital hypothyroidism is the most common treatable cause of mental retardation, requiring immediate treatment to prevent abnormal brain development. However, many of the abnormal thyroid test results are less abnormal and difficult to interpret, with a need for repeat testing and careful follow-up before initiation of treatment. Less often, neonatal hyperthyroidism is encountered. This article reviews and discusses management of thyroid dysfunction that may present in the first month after birth.