How does chronic kidney disease affect calcium and phosphate metabolism?

Chronic kidney disease (CKD) significantly impacts calcium and phosphate metabolism, primarily through mechanisms that result in secondary hyperparathyroidism and disturbances in mineral balance. As kidney function declines, the ability to excrete phosphate diminishes, leading to hyperphosphatemia (elevated phosphate levels) in many CKD patients. This high phosphate level stimulates the parathyroid glands to secrete more parathyroid hormone (PTH) in an effort to maintain calcium levels and counteract the effects of phosphate retention.

As a compensatory mechanism, elevated PTH causes increased mobilization of calcium from the bones and promotes renal calcium reabsorption, even as the kidneys struggle to manage phosphate excretion. Over time, persistent high levels of PTH can lead to bone disease due to excessive bone resorption, resulting in a metabolic bone disorder known as renal osteodystrophy.

Furthermore, with reductions in activated vitamin D (calcitriol) production by the kidneys due to CKD, intestinal absorption of calcium is impaired, which further contributes to altered calcium and phosphate balance. Therefore, the interplay between impairments in renal function, mineral homeostasis, and hormonal responses characterizes the complex relationship between CKD and mineral metabolism.

Understanding this inter