Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
18 Cards in this Set
- Front
- Back
|
Learning objectives
|
Understand the primary sources of Vitamin D
Understand the primary role of Vitamin D Understand the primary functions of parathyroid hormone Understand the basic pathophysiology that occurs in renal disease |
|
|
Calcium: uses
|
Bone formation
Cell division and growth Blood coagulation Intracellular messaging |
|
|
Calcium: distribution
|
99% bone
1% intracellular 0.10% extracellular |
|
|
Serum calcium: total calcium and distribution
|
Total calcium = protein-bound calcium + ionized calcium
+ complexed calcium 45% protein bound 50% ionized 5% complexed |
|
|
Corrected serum calcium formula
|
Corrected calcium = [(4 – serum albumin) x .8] + serum calcium
IMPORTANT |
|
|
Sources of Vit D
|
Skin
-Depends on skin color -Depends on latitude Diet -Concentrated source: liver of cold water fishes -Supplementation in milk Then converted by liver to 25-hydroxy-vitamin D Then converted by kidney to 125-hydroxy-vitamin D (calcitriol) |
|
|
Active form of vitamin D
|
Vit D converted to 25 hydroxy Vitamin D in the liver (not rate limiting)
*Calcitriol – made by conversion of 25 OH D to 1,25 OH D in proximal tubular cells |
|
|
Role of calcitriol
|
Steroid Hormone
Increase intestinal calcium absorption Increase intestinal phosphate absorption Increases calcium and phosphate resorption from bone |
|
|
Role of parathyroid hormone
|
Osteoblasts have PTH receptors (not osteoclasts)
-Stimulate osteoclast resorption Renal effects occur in the distal tubule -Stimulates calcium reabsorption -Stimulates phosphorus excretion Increase Ca and decrease P |
|
|
Phosphorus distribution
|
86% in bone
14% intracellular .03% extracellular |
|
|
Fibroblast growth factor 23: effects
|
Decreases proximal tubular phosphate reabsorption
Decreases 1,25 hydroxy vitamin D production. Decreases PTH secretion |
|
|
FGF-23 tumors
|
Tumor induced osteomalacia
Hypophosphatemia Phosphaturia Very low 1,25 OH Vtiamin D3 |
|
|
Renal failure: first major problem
|
DECREASED URINARY PHOSPHORUS EXCRETION
-OCCURS at GFR 30-60 (Stage III) |
|
|
Renal failure: second major problem
|
DECREASED CALCITRIOL PRODUCTION
Calcitriol acts as a “CHILL PILL” on the Parathyroid glands Less calcitriol means more PTH |
|
|
Renal failure: third major problem
|
INCREASED PTH PRODUCTION
Causes bone resorption |
|
|
Three things of chronic renal failure
|
Decreased phosphorus excretion
Decreased 1,25 OH Vit D (calcitriol) Increased Parathyroid Hormone |
|
|
Treating hyperphosphatemia
|
Decrease phosphorus in diet
-Avoid colas, dried beans, dairy products Use phosphorus binders with meals -Calcium carbonate or calcium acetate -Sevelamer (polymer) or lanthanum Remove phosphorus with dialysis |
|
|
Treating renal failure
|
Give calcitriol or calcitriol analogs to make up for loss of calcitriol synthesis
Give cinacalcet to bind to calcium sensing receptor of parathyroid gland And treat hyperphosphatemia |
