Challenges in Management of Lithium Induced Hyperparathyroidism: An Interesting Case

Lithium induced hyperparathyroidism occurs in 4.3% - 6.3% of patients on chronic lithium therapy compared to 0.5% -1% in general population. Lithium induced hyperparathyroidism is often an underappreciated finding and its pathophysiology often mimics other hypercalcemic disorders. Further, both medical and surgical therapy results are not very successful in long term.

Case Description:

A 60-year-old African American male with bipolar disorder on long term lithium therapy, chronic kidney disease stage 3a and hypertension, presented to our emergency department for evaluation of hypercalcemia. His calcium level on presentation was 13.2 mg/dl. This was associated with chronic fatigue. Additional significant laboratory data showed ionized calcium level of 1.63 mmol/L, normal phosphorus level of 2.3, elevated iPTH of 123.6 pg./ml, Vitamin D level of 46.6 ng/ml, urine calcium creatinine ratio of 0.07 mg/g, serum kappa/ lambda free chain ratio of 2.29 and normal lithium level of 0.6. Review of prior lab records revealed chronic hypercalcemia with corrected Ca level ranging between 10.6-11.5 mg/dl in the preceding 2 years. Technetium 99m sestamibi scintigraphy scan was negative for any parathyroid adenoma or multiglandular disease. Hypercalcemia secondary to lithium use was suspected. He was treated with intravenous fluids, calcitonin, and IV pamidronate. His lithium dose was tapered and eventually replaced with olanzapine. Treatment options including treatment with cinacalcet vs parathyroidectomy was discussed with him. Given his long-standing treatment with Li, recommendations were made for parathyroidectomy. He initially wanted to pursue surgery but later opted for medical therapy. Patient’s calcium level was normal for about a month but started to rise again. Hence, he was started on cinacalcet and is most recent calcium level is in the normal range.

Discussion:

Monitoring of parathyroid function in patients on lithium therapy is included in the revised National Institute for health and care excellence (NICE) guidelines. In addition, the International Society for Bipolar Disorder (ISBD) recommended monitoring calcium levels on initiation of lithium treatment, after 6 months, yearly thereafter. As per literature review, medical intervention including stopping lithium and adding calcimimetic drug is successful in 5 % patients only. Even recurrence rate after parathyroidectomy is noted to be between 8%- 42% in different studies. Further research to study the pathophysiology of hyperparathyroidism with lithium use and assess the effectiveness of medical versus surgical therapy is needed.