To the Editor.
—The article by Sawin et al1 in the August 1985 issue of the Archives demonstrates that screening for hypothyroidism in the elderly by measuring serum thyrotropin (TSH) levels is much more sensitive than screening by checking thyroxine levels. While this is certainly true, screening for hypothyroidism in the elderly by checking TSH levels may also miss cases of hypothyroidism. Ordene et al2 reported that when elderly patients were administered iodine to interfere with their normal thyroid function, approximately half of the patients failed to mount an increased TSH response to thyrotropin-releasing hormone, while the young control patients did. These results indicate that the true incidence of hypothyroidism in the elderly may be even higher than the 4.4% reported by Sawin et al, because elderly patients may have an impaired ability to mount a TSH response to hypothyroidism.