JOSEPH L. BLACKSHEAR, M.D.; ALVIN L. SCHULTZ, M.D.; JEROLD S. NAPIER, M.D.; DAVID D. STUART, M.D.
Patients receiving phenytoin have lower levels of serum thyroxine (T4), free T4, triiodothyronine (T3), free T3, and reverse T3 than controls. Values for serum thyrotropin (TSH) are normal, however, and these patients remain clinically euthyroid (1-6). We report a patient with primary hypothyroidism on long-term thyroxine replacement who developed clinical hypothroidism after starting phenytoin.
A 32-year-old woman consulted her physician in February 1982 because of cold intolerance and hypersomnolence. At age 13 she had been started on phenytoin for seizures; the drug was discontinued at age 23 after 10 years without a seizure. At age 28 she developed fatigue 2
BLACKSHEAR JL, SCHULTZ AL, NAPIER JS, STUART DD. Thyroxine Replacement Requirements in Hypothyroid Patients Receiving Phenytoin. Ann Intern Med. ;99:341–342. doi: 10.7326/0003-4819-99-3-341
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Published: Ann Intern Med. 1983;99(3):341-342.
Endocrine and Metabolism, Thyroid Disorders.
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