Cinacalcet for primary hyperparathyroidism

I recently saw an 87-year-old woman with hypercalcemia due to primary hyperparathyroidism. She had previous parathyroidectomy 10 years ago for the same diagnosis with subsequent resolution of hypercalcemia. However, during the past two years her serum calcium has increased.

Most recently, serum calcium has been >11 mg/dL. Her parathyroid hormone is 183 pg/mL and 25-hydroxyvitamin D is 46 ng/mL. She is frail, weak and has been falling at home. I found several bruises over her arms and chest but she could not tell me how they got there. She could not tell me how much, or even if she was taking oral calcium supplements at home.

Indeed, after she saw me she was admitted to the hospital that afternoon for dehydration. I wonder how much of her weakness and other symptoms are related to the hypercalcemia. Once she is discharged, her primary care physician plans to admit her to an extended care facility.

The question is what to do about the hypercalcemia. With her poor health, she is obviously not a candidate for repeat parathyroidectomy. The risks of surgery would outweigh the benefits. In the past, our only option for non-surgical management of hypercalcemia would have been bisphosphonate. However, this patient also has chronic renal insufficiency with an estimated glomerular filtration rate of 30 mL/min to 35 mL/min, which means that bisphosphonate is not the best choice.

Cinacalcet (Sensipar, Amgen) is a calcium mimetic agent and is FDA approved for treatment of secondary hyperparathyroidism of renal disease and also parathyroid hormone carcinoma. However, even though it is an off-label use, cinacalcet can also be very effective for management of refractory hypercalcemia of primary hyperparathyroidism.

If this woman still has severe hypercalcemia after being rehydrated, then initiating cinacalcet will be the next step. The starting dose is 30 mg orally, once-daily and can be titrated every two to four weeks as needed. I follow calcium, phosphorus, and parathyroid hormone weekly with initiation of therapy until I am sure that a stable maintenance dose has been found. Then, I monitor less often, perhaps once per month.

One problem with cinacalcet is that it is expensive. Because it does not cure the hyperparathyroidism, it must be continued indefinitely. Thus, it should be used only when surgery is not an option. I have used cinacalcet with success in a number of patients including those who are not surgical candidates and those who have failed repeated attempts at localization and surgery. Cinacalcet is well tolerated and appears to reduce parathyroid hormone and maintain normocalcemia long-term.

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