Question

In refeeding syndrome, which electrolyte abnormality is the most important and characteristic?

• A. Hypocalcemia
• B. Hypophosphatemia
• C. Hypokalemia
• D. Hyponatremia

Hint:

Insulin-driven ATP synthesis depletes which already-low anion?

Answer 1

The Correct Option is B

Step 1: Define refeeding syndrome.
It is the constellation of metabolic and electrolyte shifts that occur when nutrition (especially carbohydrate) is reintroduced to a chronically malnourished or starved patient.

Step 2: Mechanism.
Carbohydrate refeeding triggers an insulin surge. Insulin drives glucose, phosphate, potassium and magnesium intracellularly and stimulates synthesis of ATP and 2,3-DPG, which consume phosphate. In a body already depleted of total-body phosphate, this causes a sharp fall in serum phosphate.

Step 3: The hallmark abnormality.
Hypophosphatemia is the defining biochemical feature of refeeding syndrome and is responsible for its most dangerous complications — rhabdomyolysis, respiratory and cardiac failure, hemolysis, seizures and arrhythmias.

Step 4: Why the others are wrong.
Hypokalemia and hypomagnesemia also occur and matter, but they are not the signature defect. Hypocalcemia and hyponatremia are not central to the syndrome. Phosphate is the key monitored and replaced electrolyte.

Key fact: Hypophosphatemia is the hallmark of refeeding syndrome — monitor and replace phosphate, and start refeeding slowly.