salicylates and Euthyroid-Sick-Syndromes

The nursing home clinician may encounter euthyroid residents with low total serum thyroxine (T4) values associated with certain medications or nonthyroidal illness (NTI). Hypothyroidism may be incorrectly diagnosed and thyroid hormone prescribed.. We reviewed all T4 determinations and individuals with low T4 and normal thyroid-stimulating hormone (TSH) levels were identified. Pharmacy and medical records were reviewed.. We reviewed 1,153 T4 determinations and identified 22 individuals with low T4 and normal TSH values. Eight of the 22 (36%) were being treated with high-dose salicylates, 4 (18%) with phenytoin, 3 (14%) with carbamazepine, and 2 (9%) with prednisone (15 mg/day). Three residents were on two of these medications. None was on prednisone as a single medication. Eight were on none of the medications, and 5 of these had albumin values of < or = 3.2 g/dL (a marker of NTI). After a low T4 value was determined in these individuals, 6 of the 22 were placed on T4 replacement with no documentation of hypothyroidism. In 5 of these, low T4 level could be attributed to a medication effect.. Low total T4 with normal TSH levels are commonly associated with medications and NTI.

Topics: Aged; Aged, 80 and over; Carbamazepine; Euthyroid Sick Syndromes; Female; Frail Elderly; Homes for the Aged; Humans; Male; Nursing Homes; Phenytoin; Prednisone; Salicylates; Serum Albumin; Thyroid Function Tests; Thyrotropin; Thyroxine

This study examined salsalate ingestion as a model of the sequelae of acute inhibition of thyroid hormone binding to serum protein. One dose of salsalate (60-65 mg/kg) was administered to healthy volunteers. Serum salsalate concentrations peaked at 2 h (82 micrograms/mL), then declined at 8 h to 1.2 micrograms/mL. Serum total T4 (TT4) and total T3 (TT3) concentrations declined for 4 h, then recovered by 96 h, while T4 binding protein concentrations remained unchanged. TT3 was reduced to a greater extent than TT4 between 2 h and 72 h, and serum total reverse(r)T3 (TrT3) was transiently increased at 8 h. TSH concentrations fell while TT4 and TT3 fell, then recovered while TT4, TT3, and free T3, but not free T4, were still reduced. Subsequently, TSH overshot basal levels and continued to rise after 96 h while TT4, TT3, free T4, free T3, and TrT3 were all at basal levels. We postulate that an acute release of T4 and T3 from circulating transport proteins, induced by an inhibitor of binding, can result in large and rapid redistribution of T4 and T3 into tissue compartments associated with transiently reduced peripheral tissue 5'-monodeiodination and deranged TSH regulation.

Topics: Adult; Blood Proteins; Euthyroid Sick Syndromes; Female; Humans; Kinetics; Male; Models, Biological; Protein Binding; Salicylates; Thyrotropin; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse