SAT-298 A Rare Case of Hypocalcemia Associated with Chronic PPI Usage

Abstract D.H. Tran: None. J.R. Fredrick: None. R.R. Narla: None. Background: Proton pump inhibitors (PPIs) are widely prescribed in primary care and inpatient settings. We present a rare case of a young, otherwise healthy patient on chronic PPI therapy for 15 years, experiencing sudden, severe hypocalcemia on two occasions. This unusual occurrence prompted extensive investigation to eliminate alternative causes of hypocalcemia. Clinical Case: 43-year-old female with a history of IBS, GERD, stable stage 2 CKD, and PTSD who had been on omeprazole 40 mg daily since 2008. The labs from the last decade showed normal Ca levels above 9. In Summer 2023, she presented with acute confusion and perioral tingling and reported a two-month history of tingling and numbness in her fingers. Labs showed severely low levels of Ca 6.8 mg/dL (8.7 - 10.4), Mg 0.8 mg/dL (1.6 - 2.6), and K 2.4 mEq/L (3.5 - 5.1), with normal levels of PTH 54 pg/mL (19 – 88), Vit D 25-OH 35 pg/mL (30 – 130) and albumin 4.2 g/dL (3.2-4.8). She was treated with IV repletion of her electrolytes, and her PPI was discontinued. She reported resolution of her symptoms upon discharge. No further workup was initiated, and it was deemed non-PTH mediated. Several weeks later, she resumed taking her daily omeprazole again and quickly re-developed numbness and tingling. She was re-admitted for Ca 7.5 mg/dL (8.4-10.2), ionized Ca 1.9 mEq/L (2.24 - 2.6), and Mg 0.6 mg/dL (1.6-2.5). After the second hospitalization, she was told to strictly discontinue her PPI and was started on daily oral electrolyte supplementation with referral to Endocrine Clinic, without reoccurrence of her numbness or tingling in her limbs. It is interesting to consider why these electrolyte abnormalities occurred so suddenly for our patient after having stable electrolytes while being on a PPI since 2008 and why they persisted despite oral supplementation and discontinuation of her PPI. It took several months for her hypocalcemia to recover to normal levels. Her negative workup included inherited renal syndromes (ex. Gitelman’s). Her 24-hour urine studies showed appropriately low urine Ca <1.2 mg/dL and urine Mg <1.8 mg/dL, which suggested PPI usage as the etiology. The PTH levels were inappropriately normal with hypocalcemia likely due to PTH resistance from hypomagnesemia. Conclusion: Previous reports of chronic PPI usage have shown gradual lowering of Ca levels over time due to speculated impaired absorption of magnesium. It is unusual to have sudden onset severe electrolyte abnormalities needing IV repletion after many years on a PPI. This case highlights the association and clinical recognition of exploring hypocalcemia and hypomagnesemia, with magnesium depletion causing impaired synthesis, secretion, and end-organ resistance to parathyroid hormone. Calcium replacement alone can prove difficult in such settings of hypomagnesemia, therefore optimal treatment should also include repletion and normalization of magnesium levels. Saturday, June 1, 2024