Renal osteopathy

Renal osteopathy (renal osteodystrophy) is a collective name for skeletal changes within a complex disorder of phosphocalcium metabolism that occur in chronic kidney disease. Today it is classified among the three components of CKD-MBD (bone and mineral disorder in chronic kidney disease). The clinical picture is very multifaceted due to the fact that individual factors apply to each patient at a given time in different intensity. Manifestations include osteopenia, osteomalacia, secondary hyperparathyroidism and growth retardation.

Pathogenesis
Skeletal changes are caused in renal failure by three mechanisms:

Tubular dysfunction
Low pH due to renal acidosis unbinds calcium and phosphorus ions from the hydroxyapatite structure. This results in demineralization of the bone matrix and osteomalacia.

Generalized renal failure
It leads to a decrease in phosphate excretion due to insufficient renal elimination, thus resulting in chronic hyperphosphatemia. Hyperphosphatemia stimulates parathyroid glands, contributing to secondary hyperparathyroidism.

Reduced production of enzymes and growth factors
The kidneys secrete an enzyme (1-hydroxylase) that converts vitamin D into an active form and also secrete the protein BMP-7. A decrease in active vitamin D3 (calcitriol) leads to hypocalcemia and contributes to secondary hyperparathyroidism. A lack of calcitriol increases the secretion parathormone (PTH), which activates 1-hydroxylase, thereby adjusting the level of calcitriol in the blood, but hyperparathyroidism occurs. However, with progressive failure, this compensatory mechanism is insufficient and hypocalcemia occurs. BMP-7 produced by renal tubular cells induces osteoblast proliferation and differentiation. Its reduced production thus leads to osteopenia.

Related articles

 * Renal failure
 * Hyperparathyroidism
 * Osteopenia
 * Osteomalacia
 * Hyperphosphatemia