A 45-year-old man with chronic alcoholism, admitted after 7 days of poor oral intake, is started on intravenous dextrose infusion. On day 2 he develops generalised weakness, paraesthesias, dysphagia, and a serum phosphorus of 1.2 mg/dL (normal 2.5 to 4.5). What is the underlying mechanism of the hypophosphataemia?
- A Phosphate binding by excess calcium released from bone
- B Increased renal excretion of phosphate secondary to volume expansion
- C Insulin-driven intracellular uptake of phosphate for ATP synthesis ✓
- D Consumption of phosphate during glycogen catabolism in the liver
Correct answer: C. Insulin-driven intracellular uptake of phosphate for ATP synthesis
Explanation
Refeeding syndrome occurs when carbohydrate administration in a starved patient triggers insulin release. Insulin drives glucose and phosphate into cells for glycolysis and oxidative phosphorylation, depleting serum phosphate, along with magnesium and potassium. The result is impaired ATP generation causing the neuromuscular features shown. Renal excretion is reduced by insulin, not increased, so option B is wrong.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.