title: Generalized resistance to thyroid hormone associated with possible selective cardiac nonresistance.
abstract: OBJECTIVE
  To review the condition of generalized resistance to thyroid hormone and to report a case of generalized thyroid hormone resistance associated with atrial fibrillation.
  
  
  METHODS
  A case report is presented of a 52-year-old man with atrial fibrillation who was referred by a cardiologist for thyroid ablation because of "hyperthyroidism," when his free thyroxine was found to be 4.35 ng/dL (normal, 0.55 to 2.46) and his free triiodothyronine was 6.5 pg/mL (normal, 1.4 to 4.4).
  
  
  RESULTS
  This clinically euthyroid man with no signs or symptoms of hyperthyroidism except for the possibly related atrial fibrillation had a thyrotropin level of 3.45 mIU/L (normal, 0.46 to 4.7) in conjunction with the aforementioned increased levels of thyroid hormones. Further evaluation revealed normal 6-hour (11.7%) and 24-hour (27.6%) (123)I uptakes. Magnetic resonance imaging of the pituitary revealed a normal-sized gland with no masses.
  
  
  CONCLUSIONS
  This is a rare case of generalized resistance to thyroid hormone in a patient with only atrial fibrillation. Whether the heart was selectively nonresistant to thyroid hormone as the cause of his atrial fibrillation or whether his atrial fibrillation was due to his mitral valve prolapse documented on echocardiography could not be determined with certainty. His ventricular rate of 83 per minute and laboratory evaluation suggest that thyroid hormone was not the cause of the atrial fibrillation.
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, University of South Florida for Health Sciences, Tampa, Florida, USA.
authors.forename: M N
authors.initials: MN
authors.lastname: Dizon
authors.forename: A D
authors.initials: AD
authors.lastname: Henry
authors.forename: M
authors.initials: M
authors.lastname: Beeson
authors.forename: D L
authors.initials: DL
authors.lastname: Vesely
mesh_terms: D001281:Atrial Fibrillation / Q000503:physiopathology*; D006321:Heart / Q000503:physiopathology*; D006801:Humans; D006980:Hyperthyroidism / Q000503:physiopathology; D007457:Iodine Radioisotopes; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D013960:Thyroid Function Tests; D018382:Thyroid Hormone Resistance Syndrome / Q000097:blood / Q000503:physiopathology*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D007457:Iodine Radioisotopes; D014284:Triiodothyronine; D013974:Thyroxine