The Aging Thyroid

THE number and proportion of elderly people are steadily growing in western societies as a consequence of increased life expectancy and reduced birth rate. This phenomenon has important social, economical, and public health implications and has generated a number of studies aimed at clarifying the basis of the physiological and pathological aspects of aging. In this context, endocrine function in the elderly has been the object of particular attention (1–9). An important concept derived from these studies is that while the equilibrium concentrations of the principal hormones are substantially normal in most healthy elderly, with advancing age there are significant alterations in hormone production, metabolism, and action, with consequent achievement of new equilibria. As proposed by Mooradian et al. (4), aging may be defined as a time of reduced adaptability to metabolic perturbation. It has been repeatedly suggested that some of these changes may play a role in the pathophysiology of senescence, but the evidence for this is still very limited. The thyroid gland plays an important and specific role in the relationships between the endocrine system and aging (10–22). First, it is well recognized that symptoms of aging can easily be confused with hypothyroidism, and in the past decreased thyroid function was believed to be one of the hallmarks of the aging process (14,16). Second, thyroid diseases are common in the elderly, but their clinical manifestations are frequently different from those seen in younger patients; they are more subtle and often hidden by a background of intercurrent disease.