- Decreased glomerular filtration rate (GFR) leads to decreased filtration of phosphate, phosphate retention, and increased serum [phosphate]
- Increased serum phosphate complexes Ca2+ and leads to decreased ionized [Ca2+]
- Decreased production of 1,25-dihydroxycholecalciferol by the diseased renal tissue also contributes to the decreased ionized [Ca2+]
- Decreased [Ca2+] causes secondary hyperparathyroidism
- The combination of increased PTH levels and decreased 1,25-dihydroxycholecalciferol produces renal osteodystrophy, in which there is increased bone resorption and osteomalacia.