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25 Cards in this Set
- Front
- Back
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What is Calcium important in?
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1. Bone Formation
2. Cell division and growth 3. Blood coagulation 4. Intracellular messaging |
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Calcium Distribution
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99% bone
1% intracellular 0.10% extracellular |
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What are the components of Serum Calcium?
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Total calcium = protein-bound calcium + ionized calcium + complexed calcium
45% protein bound 50% ionized (The body is adjusting the free calcium that is floating around.) 5% complexed |
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What do we measure for Calcium in a BMP?
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The total calcium.
This is a problem if albumin is low, b/c ionized calcium would be the same but the protein-bound calcium is low. |
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What factors affect serum calcium?
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Albumin binding
Other protein binding pH |
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Equation for:
Corrected Serum Calcium |
Corrected Calcium =
[(4-serum albumin) * 0.8] + serum calcium this tells you what the calcium would be if their albumin was normal |
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Where does renal calcium reabsorption occur?
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Most calcium absorption occurs in the Proximal tubule although there is also some in the thick ascending loop of Henle
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What are the Calcium Hormones and their effects on serum calcium?
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Without the effects of parathyroid hormone, Vitamin D, and calcitriol:
--> Serum calcium 4 mg/dl Normal serum calcium about 8-10 mg/dl |
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How much sunlight is needed to make cholecalciferol?
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depends on skin color
(less light is required for lighter skin) depends on latitude |
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Where in the diet do we get Vitamin D?
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Concentrated source: liver of cold water fishes
Supplementation in milk |
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What is the active form of Vitamin D?
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*Calcitriol – made by conversion of 25 OH D to 1,25 OH D in proximal tubular cells mediated by 25 hydroxy Vitamin D 1-alpha hydroxylase.
(but Vit D converted to 25 hydroxy Vitamin D in the liver [not rate limiting] first) |
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What is the role of calcitriol?
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Steroid Hormone
*Increase intestinal calcium absorption *Increase intestinal phosphate absorption Increases calcium and phosphate absorption from bone ↑serum Ca ↑serum P |
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What inhibits the production of PTH?
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Ca
Mg |
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What promotes production of PTH?
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hypocalcemia
Vitamin D Lithium |
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What are the effects of Parathyroid Hormone?
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Osteoblasts have PTH receptors (not osteoclasts)
- Stimulate osteoclast resorption Renal effects occur in the distal tubule - Stimulates calcium reabsorption - Stimulates phosphorus excretion ↑ serum Ca ↓ serum P |
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Where are the parathyroid glands located?
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normally in the thyroid... but they can be left behind the sternum
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Where is phosphorous located?
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86% in bone
14% intracellular 0.03% extracellular |
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Where is most phosphorous reabsorbed?
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proximal tubule
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Fibroblast Growth Factor 23
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* helps excrete phosphorous in urine
Decreases proximal tubular phosphate reabsorption Decreases 1,25 hydroxy vitamin D production. Decreases PTH secretion |
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What is a FGF-23 Tumor?
What are the effects? |
Tumor induced osteomalacia
Effects - Hypophosphatemia - Phosphaturia - Very low 1,25 OH Vitamin D3 |
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What are the problems of Renal Failure?
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1. DECREASED URINARY PHOSPHORUS EXCRETION
- Occurs at GFR 30-60 (Stage III Kidney Dz) - Kidney is no longer able to maintain homeostasis 2. DECREASED CALCITRIOL PRODUCTION - Calcitriol acts as a “CHILL PILL” on the Parathyroid glands - Less calcitriol means more PTH 3. INCREASED PTH PRODUCTION - Causes bone resorption |
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Renal Failure
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Decreased phosphorus excretion
Decreased 1,25 OH Vit D (calcitriol) Increased Parathyroid Hormone |
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Treatment of Renal Failure
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- Treatment of Hyperphosphatemia
- Give calcitriol or calcitriol analogs to make up for loss of calcitriol synthesis - Give cinacalcet to bind to calcium sensing receptor of parathyroid gland |
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Treatment of Hyperphosphatemia
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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 |
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Cinacalcet
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drug
binds to calcium sensing receptor of parathyroid gland |
