Vitamin D and Immune Function Flashcards
(23 cards)
What does PTH stimulate?
Renal 1 alpha- hydroxylase which converts 25-hydroxycholecalciferol to 1,25 diydroxycholecalciferol which stimulates intestinal Ca++ absorption
What is the active form of vitamin D?
1,25 dihydroxycholecalciferol
What does vitamin D promote?
Mineralization of new bone by increasing both plasma Ca++ and phosphate so that they can be deposited in new bone mineral
What is vitamin D responsible for in the intestines?
1) Increases both Ca++ and phosphate absorption
2) Induces the synthesis of calbindin D-28 K
What is vitamin D responsible for in the kidney?
Increase both Ca++ and phosphate absorption
What does PTH do in the kidney?
Increases Ca++ but decreases phosphate absorption
What is vitamin D responsible for in bone?
Acts synergistically with PTH to stimulate osteoclast activity and bone resorption
Why would vitamin D stimulate bone resorption?
Mineralized “old” bone is resorbed to provide more Ca++ and phosphate to ECF so that new bone can be mineralized (aka bone modeling)
What does vitamin D deficiency cause in children?
Rickets
What happens to the bones in a child with rickets?
There isn’t enough Ca++ and phosphate available to mineralize the growing bones.
What is rickets characterized by?
Growth failure and skeletal deformities
What does vitamin D deficiency cause in adults?
Osteomalacia
What happens to bones in osteomalacia?
The new bone fails to mineralize so it softens the weight bearing bones
How can vitamin D deficiency also play a role in hyperparathyroidism?
Vitamin D deficiency can lead to hypocalcemia which in turn overstimulates the parathyroid to secrete excessive PTH secondary to hypocalcemia
What are sources of vitamin D?
1) Sunlight
2) Dietary sources like oily fish
How does sunlight provide vitamin D?
Solar UV B penetrates the skin and converts 7-dehydrocholesterol to pre-vitamin D3 which is rapidly converted to vitamin D3
Can you get too much vitamin D from the sun?
No, any excess is destroyed by the sunlight
Besides adverse effects on bone, what other diseases are associated with vitamin D deficiency?
1) CV disease
2) Cancer
3) Infection
4) MS
5) Childhood asthma
6) Tuberculosis
What cells express vitamin D receptors?
All cells
What are some functions of vitamin D?
1) Controls over 200 genes
2) Decreases cellular proliferation
3) Potent immunomodulator
4) Control inflammation
5) Muscle strength
6) Blood pressure
Are PTH levels high or low in chronic renal failure?
High (secondary response)
Can chronic renal failure cause osteomalacia?
Yes, due to deficiency of vitamin D (decrease plasma Ca++, increase plasma phosphate)
What is chronic renal failure characterized by?
Decrease production of 1,25-dihydroxycholecalciferol
