MON-358 Hypercalcemia During Teriparatide Therapy

Background: Teriparatide (TPTD) is a recombinant PTH analog used as an anabolic agent in the treatment of osteoporosis that stimulates bone formation and activates bone remodeling. The most common side effects are nausea, vomiting, hypertension and dizziness. Transient hypercalcemia is a known adverse effect which is usually seen a few hours after administration and resolves within 16 hours. However, marked late hypercalcemia is a rare event and may be of concern in clinical practice. Clinical Cases: Case 1 is a 54-year-old man with a history of osteoporosis (lumbar spine T-score of -2.8), previously treated with bisphosphonates and who had been on a course of TPTD for about 6 months in but had not been consistent in taking the medication. Prior to subsequently restarting TPTD, his initial labs were notable for a normal Ca 9.3 mg/dl (8.5 - 10.1 mg/dl), vitamin D 25 OH 49 ng/ml (30.0 - 100.0 ng/ml) and PTH 41.3 pg/ml (8.7 - 77.1 pg/ml). Six months into the treatment, he was noted to have asymptomatic hypercalcemia of 11.2 mg/dl approximately 24 hrs after the last TPTD injection. A repeat calcium of 10.7 mg/dl was obtained while still on therapy with TPTD with normal levels of vitamin D 25 OH of 45 ng/ml. Case 2 is a 75-year-old woman with a history of osteopenia and severe scoliosis, who had been on a course of raloxifene and then preventive doses of alendronate previously. Prior to starting TPTD, her Ca levels were normal at 9.3 mg/dl, PTH was 24 pg/ml and vitamin D 25 OH was 33 ng/ml. However, six months into the treatment she was noted to have elevated Ca of 12.5 mg/dl (24 hrs after the last TPTD dose), with low levels of vitamin D 25 OH of 24.2 ng/ml. Ca levels returned to the baseline of 9.3 mg/dl when TPTD was held. Conclusion: Teriparatide has a long track record of safety and does have the rare side effect of hypercalcemia. 1-3% of patients may have mild hypercalcemia after administration. Intake of calcium and vitamin D should be monitored at the start of therapy given these concerns. Although almost never a cause of discontinuation of treatment in clinical practice, it is important to be aware of this side effect in patients who may be at risk of complications of hypercalcemia.