EVALUATION OF PITUITARY AND PERIPHERAL TISSUE MARKERS OF THYROID-HORMONE ACTION IN AN IRANIAN FAMILY WITH RESISTANCE TO THYROID-HORMONE

Resistance to thyroid hormone (RTH), an inherited syndrome of reduced sensitivity to thyroid hormone, is being detected with increased frequ ency. We report the first family with RTH identified in Iran. Goiter p rompted thyroid evaluation, and nonsuppressed TSH associated with high free T-4, suggested RTH as the etiology. The mother and all four of h er children expressed the RTH phenotype associated with attention defi cit and hyperactivity. Detailed clinical and laboratory studies before and following the administration of graded doses of L-T-3 demonstrate d relatively severe resistance to the hormone at the level of the thyr otrophs and peripheral tissues. Our data underscore the importance of evaluating the changes of various parameters of thyroid hormone action in response to thyroid hormone rather than their measurement at basel ine or assessment of absolute levels.