Depression: An unrecognized presentation of hyperthyroidism in old age

It is well documented that symptoms of hyperthyroidism may be similar to those observed in patients with psychiatric disease, most commonly affective disorders. Classical manifestations reported include dysphoria, anxiety, emotional lability, tremor, restlessness and rapid speech. Overactivity of the adrenergic system caused by hyperthyroidism might explain the similarity to clinical manifestations of mania and anxiety [1]. However, hyperthyroidism can also present with symptoms more frequently described in hypothyroid states, namely suggestive of depression apathy, lethargy, fatigue, anorexia and decreased cognition. Such an atypical presentation is especially frequent in older people, and was first described as apathetic thyrotoxicosis by Lahey in 1931 [2]. The pathogenesis of depression in hyperthyroid states in less clear: prolonged hyperthyroidism might exhaust noradrenergic transmission and therefore contribute to depression [1].