Vitamin D Flashcards
Name the precursor to vitamin D3 found in the skin.
7-dehydrocholesterol
(D2/D3) has 33~50% of the biological activity of (D2/D3)
D2 has 33~50% of the biological activity of D3
This form of vitamin D is found in yeasts and fungi.
Ergocalciferol (Vitamin D2)
T or F. Supplements can contain either D2 or D3.
True
What happens to vitamin D3 (cholecalciferol) in the liver?
It undergoes hydroxylation at the 25 position to form 25-OHD3 (calcifediol).
What happens to 25-OHD3? Is this the active form?
No, it is not the active form. It goes to the kidney to hydroxylated at the 1 position to form 1,25-(OH)2D3 or Calcitriol.
Which form of Vitamin D3 is the major circulating form?
25-hydroxyD3 or Calcifediol
Which form is the active form?
Calcitriol
What is the function of vitamin D?
- Maintain serum Ca and Phosphate within narrow physiological range
- This indirectly supports normal bone mineralization, neuromuscular function and cell physiology
Name 3 ways that vitamin D increases serum Ca and Pi.
1) Increases Ca and Pi absorption by the small intestine
2) Enhances the mobilization of Ca and Pi from bone
3) Decreases Ca and Pi excretion by the kidney
How does vitamin D affect bone metabolism?
It increases RANKL production by osteoblast stromal cells, enhancing osteoclast-mediated bone resorption
Name the nuclear hormone receptor that VDR heterodimerizes with once in the nucleus.
RXR - retinoic acid X receptor
T or F. Vitamin D decreases insulin production.
False, it increases it
T or F. Vitamin D increases myocardial relaxation.
False. It increases myocardial contractility
T or F. Vitamin D inhibits renin synthesis.
True
