A cross-sectional and a prospective study of thyroid disorders in lithium-treated patients.

BACKGROUND

The effects of lithium treatment on the thyroid gland have been demonstrated in a number of studies. Most of this research is based on cross-sectional studies and prospective studies are required to confirm these observations.

METHOD

During our genetic association studies, we recruited 115 males and 159 females suffering with affective disorders who had received lithium treatment. We observed longitudinally 57 of these patients, who attended our clinic for between 1 and 7 years and had no thyroid abnormalities at baseline. We performed regular checks of thyroid antibodies, thyroid function tests and lithium levels.

RESULTS

Hypo- and hyperthyroidism, including cases that developed prior to lithium treatment, were more common in women (25.8%) than in men (8.7%) and increased with age. By the age of 65, the risk in women increased to 50%. Hypothyroidism was induced by lithium in 17% women. In the prospective study, 4 out of 33 women developed hypothyroidism (an incidence of 27.4 cases per 1000 years). One woman developed thyrotoxicosis.

CONCLUSIONS

The risk for hypothyroidism induced by lithium is especially increased in women over the age of 50. Women should be warned of the risks involved when offered lithium treatment. The frequency of lithium-induced thyrotoxicosis is very low.