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Subclinical hypothyroidism (i.e., elevated thyroid-stimulating hormone [TSH] and normal free thyroxine levels) is common, but the value of treatment remains controversial. In this U.K. randomized trial, investigators identified 737 older patients (age, ≥65) who had laboratory evidence of subclinical hypothyroidism within the previous 3 years (TSH levels, 4.6–19.99 mIU/L) and were not treated. Patients received either supplemental levothyroxine or placebo; initial levothyroxine dose was either 25 μg or 50 μg daily, depending on body weight and cardiac history, and dosing was titrated to achieve a normal TSH level (0.4–4.6 mIU/L). At baseline, mean TSH level was 6.4 mIU/L, and mean free thyroxine level was 1.03 ng/dL.
During 1 year of follow-u…