Iatrogenic Hypocalcemia With Treatment of Milk-Alkali Syndrome

Hypercalcemia is common disorder with the most likely etiology being primary hyperparathyroidism in the outpatient setting and malignancy in the hospitalized. With emergence of proton pump inhibitors and histamine blockers, milk-alkali syndrome has become a rarity. We report a unique case of hypercalcemia secondary to milk-alkali syndrome overtreated with bisphosphate therapy resulting in hypocalcemia. A 77-year-old woman with a past medical history of hypertension, gastroesophageal reflux disease presented with slurring of speech for 2 days with nausea and vomiting. Labs showed a calcium of 15.4 mg/dL, with an albumin of 4.0 g/dL. Other pertinent labs showed an ionized calcium of greater than 7.3 mg/dL, pH of 7.49, PTH of 15 pg/mL, PTHrP of 9 pg/mL, vitamin D 25-OH of 16 ng/mL, TSH of 2.16 IU/mL and acute kidney injury. Patient was started on intravenous fluids and given both calcitonin and pamidronate on presentation by the admitting team. When seen in consultation, history revealed that patient was consuming more than eight calcium carbonate antacid tablets daily and was also on hydrochlorothiazide. The calcium level decreased to 8.7 mg/dL within 48 hours. There was a concern for potential hypocalcemia due to pamidronate. Patient was advised to restart calcium carbonate 500 mg twice daily upon discharge with close follow up. However, supplementation was not started and repeat calcium was 6.7 mg/dL twelve days later. The calcium normalized within a week after starting temporary calcium supplementation. A now rare cause of hypercalcemia, milk-alkali syndrome is often overlooked in the differential diagnosis resulting in overtreatment and potentially dangerous hypocalcemia. Emergent management of intravenous hydration and bisphosphonate therapy is often immediately given by clinicians. Bisphosphonate therapy is not immediately effective and demonstrates calcium lowering effects by the second to fourth day. However, patients with milk-alkali syndrome generally improve with intravenous hydration and cessation of the causative agent. This case demonstrates the importance of obtaining a proper history with a complete list of medications and over the counter supplementations prior to treatment.