To the Editor Using the multistate life table method with data from the Rotterdam Study, Bano and colleagues,1 in a recent issue of JAMA Internal Medicine, showed that participants with low-normal thyroid function had longer life expectancy compared with those with high-normal thyroid function. Although we agree that the results of this study would contribute to reevaluating the reference range of thyroid hormones, Bano and colleagues1 need to provide more information about the association between thyroid hormone levels (within reference range) and mortality.