In chronic renal failure, the inability to produce calcitriol (1,25-dihydroxyvitamin D) leads to renal osteodystrophy. Calcitriol deficiency results in low calcium and high phosphate levels in the blood, stimulating parathyroid hormone secretion and causing demineralization of bones. To treat this, vitamin D must be accompanied by phosphate reduction through a low-phosphate diet and phosphate binders, as high phosphate levels can lead to soft tissue calcification when combined with low calcium levels.

1. BY
HARSHAD KHAN SIRAJ
GROUP 16
TBILISI STATE MEDICAL UNIVERSITY

2.  IN CHRONIC RENAL FAILURE, A CHAIN OF
EVENTS LEADS TO RENAL OSTEODYSTROPHY
 THE RENAL FAILURE RESULTS IN THE
INABILITY TO PRODUCE 1,25-
DIHYDROXYCHOLECALCIFEROL (CALCITROL)

3.  VITAMIN D IS CONSIDERED AS A PROVITAMIN
THAN VITAMIN
 CHOLECALCIFEROL (D30 IS PRODUCED FROM
SUNLIGHT IN SKIN
 THUS A LONG EXPOSURE OF SKIN IN
SUNLIGHT DOESNOT REQUIRE DIETARY
INTAKE
 CHOLECALCIFEROL IS MAINLY METABOLIZED
IN LIVER WHERE 25-
HYDROXYCHOLECALCIFEROL IS FORMED

4.  25-HYDROXYCHOLECALCIFEROL IS
CONVERTED TO BIOLOGICALLY ACTIVE 1-
α,25DIHYDROXYCHOLECALCIFEROL
 THIS IS CALLED CALCITROL
 THIS IS USUALLY DONE BY AN ENZYME 25-
HYDROXYVITAMIN D-1-α HYDROXYLASE

5.  KIDNEYS APPEAR AS A MAJOR SOURCE OF 1-
α25 DIHYDROXYCHOLECALCIFEROL
 ALSO SOME OF THE MAJOR TISSUES
INCLUDING BREAST,PROSTRATE,COLON

6.  THE REDUCTION IN LEVEL OF CALCIUM IN
SERUM RESULTS IN THE INCREASED LEVEL OF
PHOSPHATE
 RESULTING IN THE CONDITION OF
HYPERPHOSPHATEMIA
 THE SERUM PHOSPHATE LEVELS ARE OFTEN
HIGH ENOUGH TO METASTISE CALCIUM i.e
CALCIFICATION OF SOFT TISSUES
 IT TENDS TO LOWER SERUM CALCIUM LEVELS

8.  FURTHER HYPERPHOSPHATEMIA AND
HYPOCALCEMIA STIMULATE PARATHYROID
HORMONE SECRETION
 THIS CONDITION LEADS TO
DEMINERALIZATION OF BONES

11.  ADMINISTRATION OF VITAMIN D IS NOT
SUFFICIENT BECAUSE OF COMBINATION OF
HYPERPHOSPHATEMIA AND HYPOCALCEMIA
 IT LEADS TO EXTENSIVE METASTASTIC
CALCIFICATION
 THE HIGH DOSES OF VITAMIN D MUST BE
ACCOMPANIED BY PHOSPHATE REDUCTION
 BUT IT IS DIFFICULT TO TEDUCE DIRECTLY
PHOSPHATE BECAUSE MOST PROTEIN
SOURCES ARE HIGH IN CALCIUM

12.  IN THIS REGARD VEGETABLE PROTEINS IS
BETTER CHOICE THAN ANIMAL PROTEIN
 THIS IS BECAUSE VEGETABLE PROTEINS IS IN
THE FORM OF PHYTATES
 AND ARE UNAVAILABLE FOR ABSORPTION
 IT IS NECESSARY TO AVOID PROCESSED FAT
BECAUSE OF ADDING OF PHOSPHATES
 CALCIUM ACETATE AND A CATIONIC
POLYMER CALLED SEVELAMER
HYDROCHLORIDE ARE MOST COMMONLY
USED PHOSPHATE BINDER AT PRESENT

13.  ORALLY ADMINISTERED 1,25-(OH)2 D IS
EFFECTIVE AT STIMULATING CALCIUM
ABSORPTION IN THE MUCOSA
 BUT IT DOESNOT SIGNIFICANTLY ENTER
PERIPHERAL CIRCULATION
 THUS IN SEVERE HYPERPARATHYROIDISM
INTRAVENOUS 1,25(OH)2 D IS REQUIRED

14.  DEFICIENCY OF VITAMIN D ALSO LEADS TO
◦ RICKETS-IN GROWING CHILDREN
◦ OSTEOMALACIA-IN ADULTS