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

To determine the prevalence of the side effects of lithium therapy and possible predictors of hypothyroidism in women and men with bipolar disorder.

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.

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.

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.