Thyroid dysfunction, lithium-induced

Reversible hypothyroidism may occur in as many as 20% of the patients receiving lithium (Lindstedt et al. 1977 Myers et al. 1985). Lithium-induced hypothyroidism occurs more frequently in women. Thyroid function should be evaluated every 6-12 months during lithium treatment or if symptoms develop that might be attributable to thyroid dysfunction, including depression or rapid cycling. 

Lithium-induced hypothyroidism has been briefly reviewed (626). Some patients develop more persistent subclinical hypothyroidism (TSH over 5 mU/1, free thyroxine normal) and others overt hypothyroidism (higher risk in women, in those with pre-existing thyroid dysfunction, and those with a family history of hypothyroidism). Since subclinical hypothyroidism is not necessarily asymptomatic, treatment with thyroxine may be necessary in this group (627), as well as in those with more obvious hypothyroidism (628). 

The production of thyroid disorders by lithium is common and requires constant concern throughout the treatment. Lithium-induced hypothyroidism can produce depression and other mental dysfunction, greatly confusing and complicating the patient s clinical picture. 

Despite this variety of clinical findings, frank hypothyroidism and clinical goiter actually are rare sequelae of lithium therapy. However, it is difficult to predict lithium-induced thyroid dysfunction, and regular TRH determinations should be carried out to identify any late-developing disorder (43). 

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