FGF23 and secondary hyperparathyroidism: In CKD stage, decreased renal phosphorus excretion resulting from increased bone-derived fibroblast growth factor (FGF-23) and renal insufficiency, together with decreased active vitamin D synthesis, stimulates PTH secretion, which eventually manifests as secondary hyperparathyroidism, vitamin D deficiency, hypocalcemia and hyperphosphatemia [2,18].