Persisting Hypocalcemia After Surgical Parathyroidectomy: The Differential Effectiveness of Calcium Citrate Versus Calcium Carbonate With Acid Suppression

The effectiveness of oral calcium (Ca) may be contingent on a patient׳s factors beyond compliance, such as proton-pump inhibitor use and the choice of calcium supplements. A 32-year-old Hispanic male with end-stage renal disease on peritoneal dialysis underwent successful surgical parathyroidectomy (intact parathyroid hormone level: 2,328 pg/mL; postsurgical: 287-69 pg/mL [normal: 8.5-72.5]). His postoperative course was complicated by severe and recurrent hypocalcemia as outpatient and he needed repeated admissions for intravenous Ca gluconate. Initially, severe hypocalcemia (corrected Ca: 4.8-5.6 mg/dL; nadir ionized Ca: 0.57-0.69 mmol/L) was attributed solely to medical noncompliance with oral Ca carbonate (3750 mg, 3×/day between meals) and calcitriol (2-4 mcg/day). Recognizing coexisting treatment with proton-pump inhibitor, oral Ca supplement was changed to calcium citrate (2,850 mg, 3×/day) with prompt resolution of hypocalcemia (corrected Ca: 8.1-8.3 mg/dL). This current case and the included literature review emphasize the disproportionate effectiveness of Ca citrate in subjects with achlorhydria.