15. Vitamin D (cholecalciferol) Flashcards Preview

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Flashcards in 15. Vitamin D (cholecalciferol) Deck (18):
1

viamin D is also called D -active form

cholecalciferol 1.25 (OH)2

2

vitamin D- source

D3 exposure in skin, consumed in milk , fish and plants
D2 ingested from plants, fung, yeast

3

Vitamin D2/D3 - next step

both converted to 25-OH in liver and to 1.25
(OH)2 in kidney

4

Vitamin D -1 hydroxylation - area and enzyme

kidney (PCT)
1-α hydroxylase

5

vit D - function

1. increases absorption of intestinal Ca2+ and PO43-
2. enhances bone mineralization

6

vit D deficiecy causes

rickets in kids
osteomalacia in adults

7

causes of Vit D deficiency

1. malabsorption
2. decreased sunlight
3. poor diet
4. chronic kidney failure

8

24,25- (OH ) 2 D3 is

an inactive from of vitamin D

9

vit D active form

1.25 (OH)2

10

1.25 - (OH)2 regulation

1. PTH increases 1.25 - (OH)2 production
2. decreased Ca2+ increases 1.25 - (OH)2 production
3. decreased PO43- increases 1.25 - (OH)2 production
4. 1.25 - (OH)2 feedback inhibit its own production

11

1.25 - (OH)2 production is inhibited by

1.25 - (OH)2 feedback inhibit its own production

12

vitamin D vs PTH ( according target and function )

PTH --> increased Ca2+ reabsorption and decreased PO43 reabsorption in the KIDNEY
Vitamin D --> increased absorption of both Ca22+ and Po43- in the GUT

13

What are the two sources of the precursors for activated vitamin D?

Plants (D2) and sun exposure (D3, an inactive form)

14

On physical exam of a boy, you notice that he has bowed legs. You suspect that a vitamin deficiency is to blame. How do you treat him?

This is likely rickets; treat with vitamin D

15

A 27-year-old woman on dialysis presents with a fracture after a fall. What condition (due to vitamin D deficiency) could she have?

Osteomalacia

16

PTH increases Ca2+ and decreases serum PO43–. How are these effects different from 1,25-(OH)2 vitamin D's effects?

1,25-(OH)2 increases Ca2+ & phosphate levels from gut absorption and bone resorption

17

How are inactive forms of vitamin D converted to the active form?

D3 and D2 are converted to 25-OH in the liver, then to 1,25-(OH)2 (active form) in the kidneys

18

What is the difference between rickets and osteomalacia?

Rickets: vitamin D deficiency in kids (abnormally formed bone), osteomalacia: vitamin D deficiency in adults (poor bone mineralization)