Hyperthyroidism during lithium therapy for depression

To report three cases of hyperthyroidism encountered within a period of 32 months in patients receiving lithium therapy for depression.

Three detailed case reports are presented, and the related literature is discussed.

Although hypothyroidism during lithium therapy is well recognized and documented, appearance of cases of hyperthyroidism during lithium therapy is considered uncommon. The antithyroid effect of lithium through inhibition of generation of cyclic adenosine monophosphate tends to mask the underlying hyperthyroidism. Nevertheless, during a 32-month period, three cases of hyperthyroidism were encountered in patients who had received lithium treatment (900 to 1,200 mg/day) for 7 months to 17 years. These patients had symptoms of heat intolerance, palpitations, and tremor, and they were subsequently treated successfully with radioactive iodine.

Most likely, cases of hyperthyroidism that occur during lithium therapy may be under-diagnosed, underreported, or both.