Chronic hyperphosphatemia in CKD contributes to which electrolyte disturbance?

• A. Hypocalcemia
• B. Hypercalcemia
• C. Hyperkalemia
• D. Hypernatremia

Answer: (A)

Chronic kidney disease causes phosphate to accumulate in the blood (hyperphosphatemia) because the kidneys can’t excrete it effectively. This excess phosphate binds to calcium in the serum, reducing the amount of free calcium available. So, even though the body may try to compensate, the ionized calcium level falls—leading to hypocalcemia. In response, the parathyroid glands release more PTH, causing secondary hyperparathyroidism and further disturbances in calcium and bone metabolism. Hyperkalemia and hypernatremia are separate issues that can occur in CKD for other reasons, but the direct link of excess phosphate with calcium binding is what makes hypocalcemia the correct association here.