The estimated prevalence of subclinical hypothyroidism (SCH) in the general population is 3% to 8%. As the average age of the population in the United States and other countries continues to increase, the overall prevalence of SCH may also be expected to increase. Although age-related changes in thyroid function are well described, normal thyroid-stimulating hormone (TSH) reference limits, derived for age-specific populations, are not routinely used to identify thyroid dysfunction in elderly adults. Therefore, currently accepted values for the upper limit of normal of TSH may be inappropriate for diagnosing SCH in individuals aged 65 and older, resulting in potential overestimation of the prevalence of SCH in this population. This review discusses the current evidence of the effects of SCH on cardiovascular health and neuropsychiatric function in older adults. Although the results of some studies are conflicting, the overall evidence suggests that the consequences of SCH may be different for elderly adults than for younger populations. Treatment of SCH in older individuals requires special consideration with regard to thyroid hormone replacement therapy and expected clinical outcomes. Although careful identification of individuals with persistent SCH who could benefit from levothyroxine treatment is necessary, current evidence suggests that individuals with TSH levels greater than 10 mIU/L who test positive for antithyroid antibodies or are symptomatic may benefit from levothyroxine treatment to reduce the risk of progression to overt hypothyroidism, decrease the risk of adverse cardiovascular events, and improve their quality of life. After treatment is initiated, careful monitoring is essential.
Keywords: cardiovascular morbidity; cognitive function; diagnosis; elderly; levothyroxine therapy; morbidity; subclinical hypothyroidism; symptoms.
© 2015, The Authors. The Journal of the American Geriatrics Society published by Wiley Periodicals, Inc. on behalf of The American Geriatrics Society.