High incidence of occult thyroid disease among general medical ward patients

The objective of this study was to prospectively determine the efficacy of the results of routine testing of thyroid functions in patients admitted to a general medical ward. Blood for thyroid function tests was drawn on admission as part of the laboratory screening panel from 270 consecutive patients. Fifty-one were excluded due to recognition of thyroid-related problems by the clinical staff. 138 patients (63%) had normal free thyroxin (FT₄) levels, one patient had hyperthyroidism, 15 patients (6.8%) had laboratory primary hypothyroidism and 65 patients (29.6%) had equivocal results (FT₄ < 0.9 ng/dL and TSH < 5.0 mμ/L). In eight out of 31 patients in the latter group, the thyroid releasing hormone (TRH) test revealed primary or secondary hypothyroidism. A total of 55 patients (25.1%) expired within one year. The mortality rate was significantly higher among the low FT₄ patients (p < 0.01), and was independent of age and sex. We conclude that inclusion of FT₄ in a laboratory screening panel will reveal a large patient population with abnormal results. However, establishing the diagnosis requires additional tests. Therefore, screening for occult hypothyroidism among a select population, not the acutely sick, populations may be more efficient.