ODP116 Proton Pump Inhibitor Induced Hypocalcemia - An Overlooked Cause

Hypocalcemia can be caused by hypoparathyroidism, vitamin D deficiency, GI disorders, or hypomagnesemia. Proton-pump inhibitors (PPIs) which are commonly used for acid reflux symptoms can cause hypomagnesemia leading to hypocalcemia. We report an interesting case of acute hypocalcemia caused by a proton pump inhibitor. A 78-year-old female with a past medical history of follicular thyroid cancer diagnosed in 2008, s/p total thyroidectomy in 2008 followed by radioactive iodine ablation in 2009, was sent to the ER in 2019 for acute hypocalcemia with a calcium level of 6.6 mg/dL found on outpatient labs. Notably, she had no previous history of post-surgical hypoparathyroidism or hypocalcemia after her surgery in 2008. Upon initial evaluation in the ER, she presented with mild numbness, tingling, and weakness preceded by a diarrheal illness. She had concomitant hypokalemia of 3.1 mmol/L and hypomagnesemia of 1. 0 mg/dL for which she received IV and oral electrolyte repletion. She was eventually discharged on oral calcium carbonate, calcitriol, and magnesium. During her outpatient follow up, repeat labs showed persistent hypomagnesemia and low intact parathyroid (PTH) levels. Upon further review of her medication list, she reported continued daily use of omeprazole for acid reflux symptoms for the previous two months prior to her hospitalization. Her magnesium levels remained persistently low despite high doses of replacement. Given her persistently low magnesium and PTH levels, omeprazole was discontinued and she remained on calcium, calcitriol, and magnesium supplementation. Her calcium, and intact PTH levels eventually recovered to normal range and magnesium levels improved. Calcitriol was discontinued. She remained on a low dose of magnesium supplementation. In this patient, the development of her acute hypocalcemia was unlikely related to her remote history of the post-surgical thyroidectomy which occurred eleven years prior. Proton pump inhibitor use is often overlooked when evaluating causes of hypocalcemia. PPIs impair gastrointestinal absorption of magnesium through altering the TRPM6/7 channel affinity of magnesium by decreasing intestinal luminal pH. As a downstream effect, the resulting acute hypomagnesemia is thought to decrease PTH secretion as well as cause PTH resistance, which in turn decreases absorption of calcium, both by the renal and gastrointestinal route. There have been published cases that suggest these electrolyte disturbances commonly occur in elderly women with chronic PPI use. Clinicians should be aware of the effects that PPIs may have on electrolyte abnormalities. As a result, it may be reasonable to monitor magnesium and calcium levels while on a proton pump inhibitor. Presentation: No date and time listed