[Discovery, in neonatal screening, of 2 families carrying a syndrome of generalized resistance to thyroid hormones].

The syndrome of generalized resistance to thyroid hormones is being increasingly diagnosed, albeit often belatedly. In the two families described herein the diagnosis was established when moderately elevated thyrotropin levels were found upon neonatal screening of a family member. The family studies identified other affected members with a pattern indicating autosomal dominant inheritance. Clinical and laboratory findings in the neonates were consistent with normal thyroid function and no treatment was given. In one neonate, fibroblast nuclear receptor studies failed to detect decreased affinity for triiodothyronine, a finding reported in most previously published cases; the mutation in this patient was different from the one described in 1989 by Sakurai et al., consistent with the known genetic heterogeneity of this syndrome. It has been suggested recently that treatment of affected neonates with large doses of thyroid hormones is safe and effective in ensuring normal growth. The neurodevelopmental effects of this treatment are unknown. Early treatment is possible when the syndrome is detected neonatally. We therefore advocate routine T4 assays in neonates with moderately elevated TSH levels.