Hypothyroidism associated with positive results of the perchlorate discharge test in elderly patients

In 172 patients over the age of 55, determinations were made of thyrotropin concentrations in plasma. Although they showed such symptoms or signs of hypothyroidism as puffy face, dry skin, general malaise, cold intolerance, or constipation, there were no clinical indications of overt hypothyroidism. All the patients were apparently in a normal nutritional state, without any specific medication that might cause thyroid abnormalities. Seventeen (six men and 11 women, 9.9 percent) of the 172 patients, aged 58 to 83, had elevated plasma thyrotropin levels, ranging from 12.1 microU/ml to 170 microU/nl. To investigate the characteristics of hypothyroidism in the elderly, the perchlorate discharge test was performed in these patients. In 15 of the 17 patients, 123I thyroid uptake diminished markedly immediately after the administration of 1 g perchlorate. Thirteen of these 15 patients showed markedly diminished thyroxine (T4) levels in serum, whereas the magnitude of diminution in serum 3,5,3'-triiodothyronine (T3) values was small. Two patients with the negative discharge results showed normal T4 and T3 levels in serum. Four patients had a very small goiter, and the remaining 13 patients had no detectable goiter. Fifteen of the 17 patients had no detectable circulating thyroid antibodies in repeated determinations, and the histologic features of Hashimoto's thyroiditis were not found in the thyroid specimens obtained from two patients. These findings suggest the existence of hypothyroidism attributable to iodine organification defect without evidence of autoimmune thyroiditis in some cases in elderly patients.