Detection through screening of maternal thyrotoxicosis induced central hypothyroidism in newborns.

Use of a third generation TSH assay enabled extremely low values of TSH to be detected through newborn screening. The use of a supplemental free thyroxine improved testing specificity. The hypothyroidism observed is believed to be secondary to suppression of the hypothalamic-pituitary-thyroid axis by placentally transferred maternal thyroxine.