Calcium regulation Flashcards
Calcitriol is also known as?
Active vitamin D and 1,25 -dihydroxyvitamin D3 is formed in the kidneys.
Vitamin D exist in two chemical forms?
D3 produced in animals and d2 produced in plants.
Vit D3 is produced in skin of most mammalian species and is produced in excess providing they get
adequate exposure to sunlight. Excess is stored as 25(OH) However, heavily furred animals or animals
kept indoors need what?
Supplements of vitamin D3.
what are the main functions of Vit D?
- Stimulating Ca and P absorption in intestines.
- Stimulating bone calcium mobilisation.
- By increasing renal reabsorption of Ca in DCT.
Which hormones are sensitive to, and influence, body calcium and phosphorus stattis?
- Parathryroid hormone (PTH) increases Ca in blood and reduces re absorption of phosphate ions and increases phosphate levels in urine.
- Calcitriol increase absorption of Ca from the intestines.
- Calcitonin inhibits osteoclast activity in bones and inhibits renal tubular cell reabsorption of calcium and phosphate meaning they are excreted in urine. It has the opposite effect as PTH
With a diet too high in P compared to Ca what will happen?
You will get the formation of Calcium phosphate in the gut which is poorly absorbed as it is an insoluble salt, therefore a Ca deficiency may actually result from a high phosphorous level rather than low Ca.
In ruminants where is the major absorption site of Mg?
The rumen.
In non-ruminants where is the major absorption site of Mg?
Small and large intestine.
Animals with hypomagnesia are often also hypo calcaemic because?
low magnesium levels reduce the tissue sensitivity to PTH which hence effects Ca absorption.
What does calcitriol do?
Calcitriol increases the level of calcium (Ca2+) in the blood by increasing the uptake of calcium from the gut into the blood, and possibly increasing the release of calcium into the blood from bone.
Renal failure would have what effect on calcitriol?
Calcitriol is synthesised in kidney so renal failure would mean a drop in production soa lack of calcitriol leads to a lack of calcium and phosphates absorption in intestines.
A reduced concentration of Ca in plasma leads to?
Chronically elevated levels of PTH and this can enhance degradation of bone.
The pathophysiology of rubber jaw is?
As blood P levels rise (phosphate retention means Ca levels fall) so do PTH levels. The diseased kidney cannot activate Vit D so calcium cannot be absorbed from intestines into your blood, when blood calcium level drops more PTH is produced and hyperparathyroidism often develops producing more PTH.
Clinically this can lead to a condition called rubberjaw where you can manually twist jaws because there is not enough calcium in them.
