Relation between phenotype and intra-cellular thyroid hormone effect in patients with altered peripheral thyroid hormone sensitivity

OBJECTIVE We wished to ascertain whether different phenotypic appearances in patients with altered cellular sensitivity to thyroid hormones were related to the type of altered intra-cellular thyroid hormone effect. DESIGN Blood samples were obtained from two members of a family suffering from generalized thyroid hormone resistance (GTHR) for hormone assays and examination of the cellular thyroid hormone effect, and the results compared with results from other families with signs of altered peripheral thyroid hormone sensitivity. PATIENTS Two members of a family with thyroid hormone resistance and nine normal persons were studied. MEASUREMENTS Basal thyroid hormone function tests were measured. The thyroid hormone effect on mononuclear blood cells was determined by measuring the thyroid hormone stimulated oxygen consumption and glucose uptake. RESULTS The two family members appeared phenotypically normal except for nodular goitre. Thyroid hormone stimulated glucose uptake was depressed whereas thyröid hormone stimulated oxygen consumption was normal. CONCLUSION Comparison of the present results of the cellular examination in two patients with GTHR, with the results obtained in other families with altered peripheral thyroid hormone sensitivity, suggest that the classic GTHR (phenotype: normal or with goitre) is linked to impaired thyroid hormone stimulated glucose uptake, whereas in patients with osteopetrosis, the thyroid hormone insensi-tivity seems located at the mitochondrial level (impaired thyroid hormone stimulated oxygen consumption).