Re-evaluation of thyroid hormone status after long-term hormone therapy.

Once thyroid hormone is prescribed, it is usually continued throughout a persons's lifetime. It is therefore important that the diagnosis be based on the most definitive test available. In this study with a primary care population of 6,000 individuals, 24 patients were found to carry the diagnosis of hypothyroidism. A careful view of the records showed that the diagnosis was inadequately documented by current standards in 20 of these 24 individuals. A 21-day hormone withdrawal test was done in ten of the patients in whom the diagnosis was suspected, and 60 percent were found to be euthyroid. Although the number of patients was small, this does encourage the speculation that many patients diagnosed in the past as hypothyroid may in fact be euthyroid. The medical as well as economic impact of this high rate of misdiagnosis becomes apparent when the one contemplates the 15,000,000 prescriptions for thyroid hormone written annually in the United States.