Lithium side-effects and predictors of hypothyroidism in patients with bipolar disorder: sex differences

Objective: To determine the prevalence of the side effects of lithium therapy and possible predictors of hypothyroidism in women and men with bipolar disorder. Method: Twenty-two men and 38 women with bipolar disorder and taking lithium for at least 1 year, were interviewed about lithium side effects using a list of the most commonly reported symptoms. Results: The complaint most frequently reported was polyuria-polydipsia syndrome, which affected 36 (60%) of 60 patients. More men than women reported tremor (54% v. 26%, p < 0.05), but weight gain during the first year of treatment was more frequent in women than men (47% v. 18%, p < 0.05), as was the development of clinical hypothyroidism (37% v. 9%, p < 0.05). Weight gain during the first year of treatment (and not sex) was the only significant predictor of hypothyroidism. Conclusion: Weight gain during the first year of lithium treatment, in the absence of biological evidence of subclinical hypothyroidism, was the most predictive and, possibly, the first sign of hypothyroidism.