Thyroid dysfunction in the ageing patient

Thyroid dysfunction is a common endocrine disorder in the general population, with a reported prevalence of 10–15 %. This rate is higher in older adults, with an estimated prevalence of 25 % in some populations. Since elderly patients usually present more comorbidities than younger individuals, thyroid dysfunction may carry a synergistic negative health impact, mainly due to increased cardiovascular disease risk. Thyroid dysfunction in the elderly can be more difficult to diagnose due to its subtle or even asymptomatic clinical presentation, and the interpretation of thyroid function tests may be affected by drugs that interfere with thyroid function or by the coexistence of several diseases. Clinical experience shows that older people with hyperthyroidism display fewer signs or symptoms compared to younger people with hyperthyroidism. Moreover, older people with normal thyroid function tests have several clinical features of hypothyroidism. These observations suggest that there may be an age-related resistance to the actions of thyroid hormones. Laboratory experiments have consistently documented an age-related blunting of response to exogenously administered thyroid hormones. This resistance to thyroid hormones action has been attributed to reduced cellular transport of thyroid hormones. In light of these observations, along with epidemiologic studies, the diagnosis and treatment of thyroid disease in older people differ from the current treatment guidelines of younger people with thyroid disease. It is noteworthy that the age-related resistance to thyroid hormones is distinct from the congenital thyroid hormone resistance syndromes. This distinction is explained by the age-related changes in pituitary responsiveness to the feedback inhibition by thyroid hormones and reduced thyroid gland response to thyrotropin. The current evidence suggests that the age-related resistance to thyroid hormones is an adaptive process to prolong life span. In this review article, we summarize the current knowledge on the pathophysiology, diagnosis, and therapeutic management of thyroid dysfunction in elderly patients.