What is the primary cause of refeeding syndrome in TPN patients?

Rationale: A. High fat content does not directly cause refeeding syndrome; fat is less likely to trigger the electrolyte shifts seen in this condition. B. Rapid reintroduction of carbohydrates in malnourished patients stimulates insulin release, which drives phosphate, potassium, and magnesium into cells, leading to potentially life-threatening electrolyte imbalances—the hallmark of refeeding syndrome. C. Excess protein intake can strain kidney function but is not the primary cause of refeeding syndrome. D. Vitamin deficiencies, such as thiamine, can worsen complications, but the immediate trigger is the rapid carbohydrate load.