Hypocalcemia and H. pylori Gastritis: A Cautionary Tale

Abstract

Introduction Proton pump inhibitors (PPIs) are one of the most commonly prescribed medication. It is important to be mindful of the adverse reactions that can be associated with PPI's. One potential and rare complication is an acute drop in serum calcium (Ca2+). Presentations with seizure, tetany as well as respiratory distress have been described, even in the setting of a short course of PPI use. Case Report A 61-year-old female with a history of thyroidectomy and parathyroidectomy presented with complaints of generalized weakness accompanied by spasms and twitching of her upper extremities. Two weeks prior to presentation the patient underwent an upper endoscopy for dyspepsia which revealed antral gastritis and the patient was prescribed omeprazole. Gastric biopsy obtained at the time was positive for helicobacter Pylori and she was subsequently prescribed a triple therapy regimen (which she started 3 days prior to re-presentation). Electrocardiogram revealed QT prolongation and serum Ca2+ was found to be 5.7 mg/DL. Thyroid function was normal and parathyroid hormone was 2+ was normal. Of note, the patient had been taking MagCitrate and Ca2+ carbonate continuously since surgery, with no changes in dose. The patient was provided with IV Ca2+ repletion and her usual dose of Ca2+ was continued. The PPI was stopped and serial Ca2+ levels stabilized with concomitant resolution of presenting symptomatology. Discussion Physiologic gastric pH is required for absorption of certain formulations of Ca2+, such as Ca2+ carbonate. PPIs increase the gastric pH by covalently binding to gastric parietal cells and inactivating them. When gastric pH is pharmacologically increased, Ca2+ salts are not soluble; and are unable to be absorbed in the small intestine. The effect of decreased Ca2+ absorption is less pronounced if Ca2+ is taken with meals. Gastric pH decreases during meals and meal protein augments Ca2+ absorption. PPI use doesn't lower serum Ca2+ level in patient who have normal parathyroid function as PTH acts to maintain serum Ca2+. However, in parathyroidectomy patients, the only way to maintain Ca2+ levels is by consuming Ca2+ supplementation. Any factors which decrease Ca2+ absorption will limit the functional serum Ca2+. To avoid this potential complication, PPI use should be limited in patients who have undergone parathyroidectomy. If PPI use is necessary, Ca2+ citrate should be used as it doesn't require a physiologic gastric pH for absorption.