Thyroid Research Thyroid Research Archive Hyperthyroidism

Lithium therapy can cause thyroiditis and hyperthyroidism

(March 2002)

The background of the study. Lithium carbonate has antithyroid actions, and hypothyroidism and goiter are common side effects of lithium therapy. This drug also has been associated with hyperthyroidism caused by silent (painless) thyroiditis and by Graves' disease. This study examined the relationship between lithium therapy and hyperthyroidism caused by these two disorders.

How the study was done. The study subjects were 100 consecutive patients with hyperthyroidism caused by silent thyroiditis and 300 consecutive patients with hyperthyroidism caused by Graves' disease. The number of patients with hyperthyroidism and the total number of patients who had measurements of serum lithium were determined, and the frequency of both causes of hyperthyroidism among patients taking lithium was calculated.

The results of the study. Among the 100 patients with hyperthyroidism caused by silent thyroiditis, 6 (6 percent) were taking or had recently taken lithium. Among the 300 patients with Graves' hyperthyroidism, 4 (1 percent) were taking lithium. The incidence of lithium-associated silent thyroiditis and hyperthyroidism was 1.3 cases per 1000 person-years, the incidence of lithium-associated hyperthyroidism caused by Graves' disease was 1.4 cases per 1000 person-years. The combined rate is higher than the estimated rate of hyperthyroidism (0.3 to 1.2 cases per 1000 person-years) in the general population.

Nine additional patients with lithium-associated hyperthyroidism (7 with silent thyroiditis, 1 with Graves' hyperthyroidism, and 1 with toxic multinodular goiter) were identified by review of records at the same hospital. The 13 patients with lithium-associated silent thyroiditis and hyperthyroidism included 8 women and 5 men; their mean age was 34 years. Thyroid size was no more than 2 times normal in any patient. Thyroid 24-hour I-123 uptake values were low in all patients. The hyperthyroidism subsided spontaneously in the 12 patients who were followed up.

The conclusions of the study. Hyperthyroidism caused by silent thyroiditis is associated with lithium therapy more often than is hyperthyroidism caused by Graves' disease, but both are more common in lithium-treated patients than in the general population.

The original article. Miller KK, Daniels GH. Association between lithium use and thyrotoxicosis caused by silent thyroiditis. Clin Endocrinol 2001;55:501-8.