PTH and secondary hyperparathyroidism: In CKD, PTH should be interpreted in context rather than “normalized” to a fixed target; the key diagnostic signal is whether PTH is inappropriately low or inappropriately normal relative to the accompanying calcium/phosphate pattern (suggesting hypoparathyroidism, pseudohypoparathyroidism, or iatrogenic over-suppression/adynamic bone tendency), versus markedly elevated PTH with phosphate retention suggesting secondary hyperparathyroidism.