Generalized resistance to thyroid hormone (GRTH) in a family: case studies.

A familial case of generalized resistance to thyroid hormone (GRTH) is described. A 17-year-old man (case 1), who had been treated with methimazole under the diagnosis of Graves' disease and his 11-year old sister (case 2) visited our clinic for the evaluation of their thyroid function. They lacked the signs and symptoms of thyrotoxicosis in spite of extremely high serum thyroid hormone levels. Their plasma TSH levels were not suppressed, but in fact markedly increased after TRH loading. Their peripheral indices of thyroid hormone were within normal limits and were not influenced by exogenous T3 administration. Even 150 micrograms T3 administration for 7 days did not fully suppress the TRH-stimulated TSH level in case 2. The two patients thus were diagnosed to have GRTH. Sera from their father and another sister showed identical abnormalities.