- See:
-
Calcitriol
-
Hyperparathyroidism
-
Renal Failure: (
Orders for the CRF Patient)
-
Renal Spondyloarthropathy:
-
Vit D
- Effects on Adult Bone:
- abnormalities of renal function can produce profound bone disease;
- bone disease seen in renal failure is called renal osteodystrophy;
-
early stages of osteodystrophy:
- effects on bone are primarily due to
action of parathyroid hormone on osteocyte-osteoblast
lining cell system, which is probably result of decreased phosphate excretion by the kidney;
- w/ decreased phosphate excretion, there is elevation of plasma phosphate & complexing
of calcium & phosphate in bone fluid;
- as result, increasing amounts of PTH hormone are required to move the same amount of
calcium from bone in order to maintain the plasma calcium at a constant level;
- due to elevated parathyroid hormone levels, there is increase in number of
bone remodeling centers
& increase in bone turnover;
-
late stages:
- when the glomerular filtration falls below 25% of normal, increased secretion of PTH is no
longer able to maintain normal phospate levels, and the serum
phosphate increases;
- mineralization of previously
osteomalacic bone then occurs, and
osteosclerosis develops; (see
ossification of soft tissue);
-
end stages:
- diminished ability of kidney to hydroxylate vit D leads to a decrease in circulating levels of
1,25(OH)2D3 & produces decrease in intestinal calcium absorption;
- calcification of osteoid is inhibited owing to deficiency of 1,25(OH)2D3, and owing to metabolic
acidosis and other circulating inhibitors of mineralization that occur in uremic state;
- net effect of renal dz on bone:
- is combination of secondary
hyperparathyroidism,
osteomalacia, and osteosclerosis;
- when bone disease becomes severe, pathologic fractures may occur, esp in ribs, pelvis, and hips;
- uremic pts w/ advanced hyperparathyroidism appear prone to nontraumatic
aseptic necrosis of the hips;
- bone pain, frx, and concomitant muscle disease may be the major impediment to rehabilitation in chronic uremia;
- Effects in Children:
- bone may appear diffusely sclerotic;
- varus deformity of the proximal femurs may occur as a result of bone softening and
osteomalacia;
- growth plates are widened and zone of
provisional calcification is poorly defined;
