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Variable Effects of Nonsteroidal Antiinflammatory Agents on Thyroid Test Results

Division of Endocrinology, Diabetes, and Clinical Nutrition (M.H.S., K.P.), Oregon Health and Science University, Portland, Oregon 97201; Quest Diagnostics Nichols Institute (D.A., J.C.N.), San Juan Capistrano, California 92690; and Departments of Medicine and Pathology (J.C.N.), Loma Linda University School of Medicine, Loma Linda, California 92354

Address all correspondence and requests for reprints to: Dr. M. H. Samuels, Oregon Health and Science University, Division of Endocrinology, Diabetes and Clinical Nutrition, 3181 SW Sam Jackson Park Road, Mail Code CR 107, Portland, Oregon 97201. E-mail: samuelsm{at}ohsu.edu.

To investigate the effects of nonsteroidal antiinflammatory drugs (NSAIDs) on thyroid tests, 25 healthy subjects underwent a single-dose study and/or a 1-wk study. In the single-dose study, subjects received a single dose of one of six NSAIDs (aspirin, salsalate, meclofenamate, ibuprofen, naproxen, or indomethacin) at 0800 h. Total and free thyroid hormones and TSH were analyzed 0, 1, 2, 3, 4, and 8 h later. In the 1-wk study, subjects received one of six NSAIDs for 7 d. Thyroid hormones and TSH were analyzed at 0800 h each day. Total T₄ and total T₃ were measured by RIA, free T₄ and free T₃ were measured by equilibrium dialysis, and TSH was measured by immunometric assay. There were no changes in any hormones after a single dose or 1 wk of ibuprofen, naproxen, or indomethacin. Single-dose aspirin or salsalate decreased, whereas meclofenamate increased, various total and free thyroid hormone measurements. One week of aspirin or salsalate decreased total T₄, free T₄ (salsalate only), total T₃, free T₃, and TSH. These data confirm that aspirin, salsalate, and meclofenamate affect total and free thyroid hormone measurements and identify three NSAIDs that did not change thyroid tests. TSH remained within the normal range during acute or 1-wk administration of all of the NSAIDs.

This work was supported by Grant NIH R29 DK 48366 and the Oregon Health and Science University General Clinical Research Center (Grant NIH GCRC M01-RR00334).

Abbreviation: NSAID, Nonsteroidal antiinflammatory drug.