NEONATAL SCREENING LED TO THE DISCOVERY O F 2 NEW FAMILIES WITH GENERALIZED RESISTANCE TO THYROID-HORMONES

The syndrome of generalized resistance to thyroid hormones is being in creasingly diagnosed, albeit often belatedly. In the two families desc ribed herein the diagnosis was established when moderately elevated th yrotropin 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 fin dings in the neonates were consistent with normal thyroid function and no treatment was given. In one neonate, fibroblast nuclear receptor s tudies failed to detect decreased affinity for triiodothyronine, a fin ding reported in most previously published cases ; the mutation in thi s patient was different from the one described in 1989 by Sakurai et a l., consistent with the known genetic heterogeneity of this syndrome. It has been suggested recently that treatment of affected neonates wit h large doses of thyroid hormones is safe and effective in ensuring no rmal growth. The neurodevelopmental effects of this treatment are unkn own. Early treatment is possible when the syndrome is detected neonata lly. We therefore advocate routine T4 assays in neonates with moderate ly elevated TSH levels.