Lithium-induced subclinical hypothyroidism: Review of the literature and guidelines for treatment

Background: This review addresses the definition, prevalence, etiology, and clinical significance of lithium-associated subclinical hypothyroidism and offers guidelines for evaluation and treatment of this condition. Data Sources: MEDLINE was used to search all articles written in English fr om 1964-present that included the words lithium and thyroid; lithium and su bclinical hypothyroidism; mood and thyroid function; and bipolar illness an d thyroid function. Study Findings: Lithium interferes with thyroid metabolism and increases th e incidence of overt and subclinical hypothyroidism. Subclinical hypothyroi dism may be associated with the presence of somatic and neuropsychiatric sy mptoms and interfere with treatment responsiveness. Conclusion: A careful assessment of thyroid function is recommended prior t o initiating lithium treatment and during maintenance treatment. Recommenda tions regarding the threshold for initiation of thyroxine supplementation i n patients with lithium-associated subclinical hypothyroidism are discussed in relationship to the degree of detrimental effects potentially associate d with thyroid dysfunction.