[Prevalence of deficiency of thyroxine-binding globulin (TBG)].

During 3 years 1632 newborns from Gorgas Army hospital had their cord blood screened for congenital hypothyroidism by determining serum thyroxine levels (T4). Fifty-five had serum levels below 7 mcg/dl and 80% of them went into a confirmatory evaluation for hypothyroidism. Three of those (1.8/1000 live birth) had a familiar deficiency of thyroid binding globulin (TBG). All of them were male newborns born at 38 weeks of gestation. The average T4 from the umbilical cord was 2.4 +/- 1.3 mcg/dl. This value was significantly lower than the values from those with an initial T4 below 7 mcg/dl who did not have TBG deficiency. The prevalence of TBG deficiency in this study was about 10 times higher than the prevalence reported by other authors for both the general population and the male population.