Vitamin D Flashcards
What are the factors affecting Vit D synthesis
Melanin, UVB, Age, UVB shielding
Where does Vit D synthesis begin
The skin
What “pushes start button” in Vit D synthesis
The sun
What molecule begins Vit D synthesis in skin
Cholesterol
Acetyl CoA and Cholesterol create which form of Vit D in the skin
proVitD3 - 7-Dehydrocholesterol
ProVitD3 + UVB =
PreVitD3
PreVitD3 + Skin Temp =
Vitamin D3
What is the animal source of VitD3
Cholecalciferol
What is the plant source of Vitamin D
Ergocalciferol - VitD2
Why is VitD2 “not as good” as VitD3
Does not stay in the blood as long
VitD3–>Circulation–>Liver–>25-OHase =
25(OH)D3
What enzyme converts VitD3 to 25(OH)D3?
25-OHase
What converts ProVitD3 to PreVitD3
UVB
What is another name for ProVitD3
7-Dehydrocholesterol
What converts PreVitD3 to Vitamin D3
Skin temperature
25(OH)D3 –>1-OHase in kidney =
1,25(OH)2D3 - Calcitriol
What is the active form of Vitamin D
Calcitriol - 1,25(OH)2D3
What enzyme converts 25(OH)D3 to Calcitriol
1-OHase
Where does 1-OHase convert 25(OH)D3 to Calcitriol
Kidneys
How is Vitamin D status measured (form)
25(OH)D3
When is it best to measure Vitamin D status
End of winter (storage in adipose used up)
Where is Vitamin D stored
Adipose tissue
When will Vitamin D status be highest
August/September
What can cause Vitamin D deficiency (organs)
Liver/kidney failure
What is a treatment for Vitamin D deficiency (organ failure)
Calcitriol Rx (active form)
What is a function of calcitriol in the kidneys
Increase calcium resorption (less excreted)
Why don’t VitD and Calcium need to be taken at the same time
VitD still has to be activated, first to Calcitriol, then process to form Calbindin protein
How is VitD absorbed
Follows the route of lipids
How is VitD excreted
> 70% feces, urine
What is the UL for VitD
4,000IU
What is caused by VitD deficiency in children
Rickets
What is caused by VitD deficiency in adults
Osteomalacia
What are the symptoms of rickets
Bones don’t mineralize, bone still trying to grow, legs show symptoms because support body weight, growth retardation
What are the symptoms of Osteomalacia
Poor bone mineralization; bones translucent
What are food sources of VitD
Egg yolk, beef, tuna cheese, mushrooms, tofu, fortified milk
What is the RDA for VitD 1-70years
600IU
What is the RDA for VitD 70+years
800IU
What is the Natl Osteoporosis Found recommendation for VitD 50+years
800-1000IU
Why does sun over-exposure not result in VitD toxicity
too much UVB will destroy preVitD3
What is VitD (Calcitriol) “claim to fame”
Calcium Homeostasis: Calcium absorption in enterocyte; Calcium resorption in kidney; Calcitriol, 24R,25(OH)2D3 & bone
What are functions of VitD other than Calcium homeostasis
Cell differentiation, proliferation and growth-May prevent abnormal cell growth(cancer); Blood pressure, insulin secretion, autoimmune disorders; Blood volume control
What is a symptom of VitD deficiency in children other than Rickets
Seizures
