Vitamin D Flashcards
Vitamin D is fat soluble….True or Flase?
True
Name the 2 forms of vitamin D
D2, D3
Where is Vitamin D3 (cholecalciferol) made?
In the skin
Where do you find vitamin D2 made (ergocalcifero)?
Plants
Parathyroid hormone secreted by the parathyroid glands in response to a low concentration of __________ in the blood
Calcium
Vitamin D3 is converted in the kidneys…True or False?
False, it is converted in the liver
What is the prehormone of Vitamin D3?
25-hydroxy vitamin D (calcidiol)
What happens in the kidney to 25-dihydroxy vitamin D (calcitriol)
It acts like steroid hormone
Vitamin D is also a secosteroid hormone? True or False
True
What is vitamin D responsible for?
Maintaining a normal concentration of calcium and phosphate in the blood
Name a few things Vitamin D, Calcium and phosphate in the blood are responsible for….?
- Mineralisation of bone
- Muscle contraction
- Nerve conduction
- General cellular function, there are receptors for calcitrol in 30 tissues in the body
- Possible regulation of over 1000 genes
- calcium regulating hormone, a secosteroid
- Regulates transcription of cell proteins in: osteoclasts (bone resorption) enterocytes (gut wall cells) and keratinocytes (skin)
Who is at risk of deficiency?
- Infants
- Adolescents
- Pregnant women
- Elderly
- Vegetarians
- Those not exposed regularly to sunlight, esp in high latitudes
- People with dark skin at high latitudes
How many minutes of UV exposure will meet your daily Vitamin D needs?
About 30 min exposure of face and arms if living between 42° N and 42° S
What can affect the amount of Vitamin D you are exposed to?
- Latitude and season
- Age: skin thins in the elderly, so less effective
- Skin pigmentation: dark skin protective, but not in high latitudes
- Clothing: degree of coverage and thickness
- Use of sunscreen
Rickets, Osteomalacia, Osteoporosis and all what forms of what?
Vitamin D deficiency diseases
How do we control rickets?
Fortification
Supplements
Diversification = behaviour change
Where is 1% of calcium found?
Teeth and extracellular fluid, which is important for cell function
How do we lose calcium?
Filtered from blood in kidney and then most resorbed
In urine (min 140 mg/d)
Skin, hair nails (40 – 80 mg/d)
70% of calcium is absorbed when intake is high or low?
Low
Endocrine, paracrine and autocrine are all actions of…..
Vitamin D
What is the metabolic pathway of vitamin d?
7-de hydrocholesterol converted through the skin to cholecalciferol —> converted in the liver to calcidol —> converted in kidney to calcitrol
MAINTAINS CALCIUM AND PHOSPHATE HOMEOSTASIS
