Resistance to thyroid hormones. A disorder frequently confused with Graves' disease

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Abstract
Five patients from 2 unrelated families had goiter and elevated serum concentrations of thyroxine (T4) and triiodothyronine (T3) without symptoms or signs of hyperthyroidism. All had measurable concentrations of TSH, and in 4 who were tested, there was an increase in TSH concentration following TRH administration. These 5 patients are believed to have general resistance to the effects of thyroid hormones and need elevated concentrations of T4 and T3 to maintain a eumetabolic state. Study of nuclear T3 receptors from cultured fibroblasts of 1 patient disclosed a normal equilibrium association constant and a maximal binding capacity that was greater than normal control values. Thyroid hormone resistance in this patient is not due to a decrease in either the affinity or the number of specific nuclear T3 receptors. This disorder can easily be confused with Graves'' disease and result in inappropriate treatment for hyperthyroidism, as was the case in 3 of the patients.