title: Hyperthyroxinemia in patients treated with high-dose propranolol.
abstract: Six patients with hyperthyroxinemia (five men and one woman) were evaluated for possible hyperthyroidism. All were taking large daily doses of propranolol--480 +/- 155 (+/- SE) mg--for treatment of angina pectoris. The patients had no clinical evidence of hyperthyroidism, although three had small goiters. Further evaluation of the patients revealed elevated serum free thyroxine levels and/or free thyroxine index, low-normal serum triiodothyronine levels, and elevated serum reverse triiodothyronine levels in all six. The thyroid-stimulating hormone response to thyrotropin-releasing hormone was normal in two patients, subnormal in three patients, and absent in one patient. One patient was restudied while receiving low-dose propranolol (80 mg a day), with normalization of all thyroid functional parameters. The data suggest that the abnormalities seen in patients taking high doses of propranolol were due to drug-induced blockade of iodothyronine deiodination. Signs and symptoms of hyperthyroidism are lacking in patients taking large doses of propranolol. If such a patient is discovered to have an elevated serum thyroxine level, a more complete evaluation of thyroid function is necessary before the diagnosis of thyrotoxicosis can be made. The thyrotropin-releasing hormone test may be of particular value in this circumstance.
mesh_terms: D000368:Aged; D000787:Angina Pectoris / Q000188:drug therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011433:Propranolol / Q000009:adverse effects* / Q000627:therapeutic use; D013973:Thyrotropin-Releasing Hormone / Q000097:blood; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood; D014285:Triiodothyronine, Reverse / Q000097:blood
chemical_list: D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013973:Thyrotropin-Releasing Hormone; D011433:Propranolol; D013974:Thyroxine