EFFECTS OF COMMONLY PRESCRIBED NONSTEROIDAL ANTIINFLAMMATORY DRUGS ON THYROID-HORMONE MEASUREMENTS

PURPOSE: To assess the effects of nonsteroidal anti-inflammatory drugs (NSAIDs) on thyroid function tests. PATIENTS AND METHODS: Eighty-nine patients receiving NSAIDs and 22 control subjects not taking NSAIDs were studied in a cross-sectional survey at Veterans Affairs and University hospitals. Measurements of serum thyroxine (T4), free T4 index, triiodothyronine (T3), and thyrotropin (thyroid-stimulating hormone [TSH]) were obtained for all subjects. RESULTS: Serum T4 measurements were lowered only in salsalate-treated patients, while serum T3 was depressed in patients receiving salsalate, diclofenac sodium, and naproxen. Serum T4 and T3 were unchanged in patients treated with diflunisal, ibuprofen, indomethacin, piroxicam, or sulindac. Serum TSH was normal in all subjects. CONCLUSIONS: Several NSAIDs can lower serum thyroid hormone concentrations, principally by interfering with the binding of T4 and T3 to serum carrier proteins; patients taking these drugs remain euthyroid. Awareness of these interactions may prevent unnecessary diagnostic or therapeutic interventions.