Alpha-fetoprotein in congenital hypothyroidism

alpha-Fetoprotein (alpha-FP) was measured in dried blood spots from normal, congenital hypothyroid (CH) and transient hyperthyrotropinemic (TH) newborns as well as in serum from CH and TH babies together with thyroxine, triiodothyronine and thyrotropin. The half-life of alpha-FP had a median value of 12 days in the CH cases and 4.9 days in the TH cases. alpha-FP was significantly higher in the CH group before treatment and showed a significant rise after discontinuation of thyroxine therapy. It would appear that thyroid hormones influence alpha-FP metabolism and that a hypothyroid environment results in increased alpha-FP levels.