A chronic alcoholic with pancreatitis has serum calcium 6.5 mg/dL that fails to rise despite repeated intravenous calcium gluconate infusions. Serum magnesium is 0.9 mg/dL (low). What best explains the refractory hypocalcemia?
- A Severe hypomagnesemia impairing PTH secretion and causing peripheral PTH resistance ✓
- B Excess urinary calcium excretion caused by alcohol diuresis
- C Saponification of calcium in necrotic pancreatic fat
- D Reduced intestinal calcium absorption due to steatorrhea
Correct answer: A. Severe hypomagnesemia impairing PTH secretion and causing peripheral PTH resistance
Explanation
Severe magnesium depletion blocks both the release of PTH from parathyroid chief cells and the responsiveness of bone and kidney to PTH, so even infused calcium is lost and hormone-driven reabsorption cannot be recruited. Correcting the magnesium is mandatory before calcium will normalize. Pancreatic saponification contributes modestly in acute pancreatitis but does not explain true refractoriness here.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.