Should subclinical hypothyroidism or subclinical hyperthyroidism be treated in the elderly?
Subclinical hypothyroidism in individuals < 65 years of age is associated with increased ischemic heart disease and cardiovascular mortality; however, in several meta-analyses of studies in elderly patients, these risk associations were not found. In addition to the diagnostic dilemma posed by the absence of appropriate age-specific TSH ranges, a large proportion (> 40%) of elderly patients with mildly elevated serum TSH levels may revert to euthyroidism after 4 years of follow-up without treatment. Some data suggest that levothyroxine treatment should be considered in older patients with serum TSH levels > 10 mIU/L and who have positive antithyroid antibodies or are symptomatic, to reduce the risk of progression to overt hypothyroidism, decrease the risk of cardiovascular events, and improve quality of life. This begs the question of what the appropriate TSH target level should be for patients being treated for overt hypothyroidism. The goal should be to avoid subclinical and overt hyperthyroidism and, based on epidemiologic studies, a TSH level of 4 to 6 mIU/L is a reasonable target in the elderly. Further guidance on treatment of the elderly with subclinical hypothyroidism should be generated by RCTs.
Recent studies have shown that a large proportion of older patients with subclinical hyperthyroidism (∼40%–50%) will also revert to euthyroidism with observation (within 2–7 years), whereas < 10% of patients progress to overt hyperthyroidism. Elderly patients with subclinical hyperthyroidism have been shown to have an increased risk for the development of atrial fibrillation and osteoporotic fractures. Some studies in high-risk elderly patients with persistent subclinical hyperthyroidism have shown increased risk for heart failure hospitalizations, nonfatal CVD and dysrhythmias, whereas other studies have not shown an association with CVD mortality. Work-up for the cause of subclinical hyperthyroidism in older patients is the same as that for younger patients. Whether and how to treat subclinical hyperthyroidism in older adults should be based on the risks and benefits of treatment vs. no treatment.