Vitamin D

Question 1

What general advice should be given on vitamin D and supplementation?

Answer 1

Most people are deficient in the winter

About half are deficient all year

Question 2

How much sun should people aim to get for Vitamin D?

Answer 2

Daily for approx 15 minutes with forearms, hands or lower legs uncovered without sunscreen from late march to September.
11am - 3pm

Question 3

What are the dietary sources of Vitamin D?

Answer 3

10-15%

Oily fish
Liver
Egg yolk
Mushroom
Dairy products 
Fortified foods

Question 4

Who is at risk of Vitamin D deficiency?

Answer 4

Low sunlight - housebound, dark skin, clothing.
Renal failure
Drugs - anti-convulsants

Question 5

What is vitamin D synthesised from?

Answer 5

Cholesterol

Question 6

Describe how vitamin D is made into active form?

Answer 6

Cholesterol precursor in the skin turned into cholecalciferol.
Turned to 25-hydroxy-vitamin D3 in the liver.
In kindey turned into 1-25-dihydroxyvitamin D.

Question 7

What is vitamin D required for in the gut?

Answer 7

The absorption of calcium.

Question 8

What happens in vitamin D deficiency?

Answer 8

Reduced dietary calcium absorption, low serum calcium. Activates the parathyroid to release PTH which stimulates bone resorption –>
Secondary hyperparathyroidism

Question 9

What would you expect in mild vitamin D deficiency?

Answer 9

Increased bone turnover

Increased osteoporosis risk

Question 10

What would you expect in more severe vitamin D deficiency?

Answer 10

Demineralisation
Osteomalacia in adults
Rickets in children

Question 11

What stain may be used to identify osteomalacia?

Answer 11

Masson-goldner stain

Shows demineralised bone

Question 12

What vitamin D levels are considered deficient and sufficient?

Answer 12

Sufficient >50 nmol/l
Insufficient 25-50 nmol/l
Deficient <25 nmol/l

Question 13

What advice is given about intake?

Answer 13

Reference intake 10 micrograms per day, throughout the year, for everyone >4
Unlikely to get from environment or diet
So most people should take a Vitamin D supplement

Question 14

How can you differentiate between osteoporosis and osteomalacia?

Answer 14

Both low BMD

Osteoporosis - reduced amount of bone with structural deterioration

Osteomalacia - normal amount of bone, but matrix unmineralised and soft

Question 15

What are the symptoms of osteomalacia in adults?

Answer 15

Bone pain
Fracture
Fatigue
Weakness

Question 16

What investigations could be done to investigate osteomalacia?

Answer 16

Serum calcium 
Serum vitamin D 
Serum alkaline phosphatase
Serum urea and creatinine
Bone x-rays
DXA

Question 17

What is the biochemistry of osteomalacia?

Answer 17

Low vit D, reduced calcium absorption in the gut
Serum calcium falls
PTH stimulated
Increased bone turnover and renal absorption
High alkaline phosphatase (turnover) and low urine calcium

Question 18

What is the treatment of Vitamin D deficiency?

Answer 18

High dose vitamin D
Colecalciferol 20,000 units
Calcium supplements
Long term low dose supplementation