Thyroid Function in Aging: A Discerning Approach

Abstract

Thyroid disease, increasingly common among the general population, is also rising among the elderly, which, given that the global population is aging, constitutes a serious public health issue that needs to be urgently addressed. The most common thyroid disease in younger and older individuals alike is hypothyroidism, including subclinical (SCH) and overt disease. Since TSH tends to increase with age due to intrinsic changes of thyroid metabolism and the gradual resetting of the hypothalamic-pituitary-thyroid axis, the diagnosis of “true” hypothyroidism is challenging, another difficulty being distinguishing disease-specific from aging-associated clinical symptoms. Hypothyroidism in the elderly may cause or exacerbate macrocytic anemia, hypercholesterolemia and kidney dysfunction, therefore careful clinical and biochemical control is necessary. Meanwhile, as an increase of TSH in the old and very old has been associated with longevity, a resetting of the TSH normal range according to age is strongly required before any diagnosis is made and treatment is implemented. Levothyroxine, which remains the treatment of choice, should be initiated in the old at TSH>10 mIU/l, starting with 25 μg/daily followed by cautious upward titration. Recent data (the TRUST study) revealed that treatment of SCH in the elderly does not improve hypothyroid symptoms and the tiredness score when compared with a placebo group. Hyperthyroidism is associated with increased mortality in the aged, this dependent upon type and adequacy of treatment. Treatment should be seriously considered in older patients who have endogenous subclinical hyperthyroidism with a TSH between 0.1 and 0.4 mIU/L, with regular monitoring being strongly advised.