Teriparatide Associated Late Hypercalcemia: A Report of Two Cases and Literature Review.

Introduction: Teriparatide, recombinant human parathyroid hormone (1-34), is a safe and usually well-tolerated medication. We describe two cases of late-onset hypercalcemia associated with teriparatide use and report current evidence of hypercalcemia during the treatment with PTH analogs.

Case Report: Case 1 is a 54-year-old man with a history of osteoporosis, previously treated with 6 months of teriparatide, but had not been consistent in taking the medication. Before restarting teriparatide, his serum calcium, PTH and vitamin D were normal. Six months into the treatment, he developed asymptomatic hypercalcemia of 11.2 mg/dL 24 h after the last dose. Repeat serum calcium was normal and treatment was continued. Case 2 is a 75-year old woman with a history of osteopenia and severe scoliosis. Before starting teriparatide, her calcium, PTH and vitamin D were normal. Six months into the treatment, she developed asymptomatic hypercalcemia of 12.5 mg/dL. Teriparatide was held and subsequently her serum calcium normalized.

Discussion: Transient hypercalcemia can occur during treatment with teriparatide and usually resolves within 16 h after administration. Late hypercalcemia, occurring more than 24 h after the dose, is rarely seen. It is usually mild, asymptomatic and rarely occurs repeatedly. Hypercalcemia occurs more often in patients with pre-existing hypercalcemia or vitamin D deficiency. It is rarely a cause of treatment disruption (0.18-4%).

Conclusion: Clinicians should be aware of this side effect, especially in patients who may be at risk of complications of hypercalcemia.