To the Editor.
—The article by Rosenthal et al1 and the subsequent correspondence2 prompted us to contribute to the discussion about the significance of thyroid antibodies in the evaluation of subclinical hypothyroidism in the elderly. We have determined the following factors in the serum of 115 consecutive subjects (59 women and 56 men) with a mean age of 76 years (range, 60 to 94 years) and no clinical evidence of thyroid disease or any acute illness: thyroid microsomal antibody (by both radioimmunometric and immunofluorescence techniques), baseline serum thyrotropin level, and thyroid hormones (triiodothyronine, thyroxine, free triiodothyronine, and free thyroxine).We found high titers (≥1:10 by immunofluorescence and >50 U/mL by the radioimmunometric method) of thyroid antibodies in seven of the subjects (in six women and one man). Thyroid hormone levels of antibody-positive and antibody-negative subjects were similar. Serum thyrotropin level was abnormal (>5 mU/L [>5 μU/mL]) in one