Lithium May Lead to Hypercalcemia

By Corinna Underwood

Lithium may, in some cases lead to hypercalcemia. Parathyroid hormone (PTH) and vitamin D regulate calcium balance in the body. PTH is produced by the parathyroid glands — four small glands located in the neck behind the thyroid gland. Vitamin D is obtained from exposure of skin to sunlight, and from dietary sources such as fortified dairy products, egg yolks, fish, and fortified cereals.

The drug lithium, used in treating bipolar disorder, may increase PTH release and cause hypercalcemia. A genetic mutation that affects the body’s ability to regulate calcium is seen in familial hypocalciuric hypercalcemia (FHH), a benign (non-cancerous) condition.

It is suggested that for patients with bipolar disorder on lithium treatment, health care providers should do the following:

• Monitor serum lithium levels normally every 3 months.
• Monitor older adults carefully for symptoms of lithium toxicity, because they may develop high serum levels of lithium at doses in the normal range, and lithium toxicity is possible at moderate serum lithium levels.
• Monitor weight, especially in patients with rapid weight gain.
• Undertake more frequent tests if there is evidence of clinical deterioration, abnormal results, a change in sodium intake, or symptoms suggesting abnormal renal or thyroid function such as unexplained fatigue, or other risk factors, for example, if the patient is starting medication such as ACE inhibitors, non steroidal anti-inflammatory drugs, or diuretics.
• Arrange thyroid and renal function tests every 6 months and more often if there is evidence of impaired renal function.
• Initiate closer monitoring of lithium dose and blood serum levels if urea and creatinine levels become elevated, and assess the rate of deterioration of renal function. The decision whether to continue lithium depends on clinical efficacy, and degree of renal impairment; prescribers should consider seeking advice from a renal specialist and a clinician with expertise in the management of bipolar disorder on this.
• Monitor for symptoms of , including paraesthesia, ataxia, tremor and cognitive impairment, which can occur at therapeutic levels.