Vit D Def

Question 1

What is the metabolism of Vit D?

Answer 1

UVB from sunlight is converted into cholecalciferol by skin/
Fish oil and eggs contain cholecalciferol

Liver hydroxylates it into calcidiol which is further hydroxylated in kidneys to form
CALCITRIOL(active vit D)

PTH active during low calcium levels
Causes bone resportion
stim kidneys to produce more VIT D

EFFECTS OF VIT D( increases blood calcium)
enhancing GI absorption of calcium and phosphate enhancing renal resorption calcium and phosphate.
Decreases bone resportion

Question 2

Define rickets

Answer 2

failure in mineralization of the growing bone or osteoid tissue.

Failure of mature bone to mineralize is osteomalacia.

Question 3

*Causes of rickets

Answer 3

Nutritional (primary) rickets – risk factors

• Dark skin & Decreased exposure to sunlight
• Maternal vitamin D deficiency
• Diets low in calcium, phosphorus, and vitamin D,
  e. g. exclusive breastfeeding into late infancy or, rarely, toddlers on unsupervised ‘dairy-free’ diets
• strict vegan diets

Intestinal malabsorption
• Small bowel enteropathy (e.g. coeliac disease)
• Pancreatic insufficiency (e.g. cystic fibrosis)

Defective production of calcidiol
• Chronic liver disease

Increased metabolism of calcidiol
• Enzyme induction by anticonvulsants (e.g. phenobarbital)

Defective production of calcitriol
• Chronic kidney disease
• Fanconi syndrome (renal loss of phosphate) •

Question 4

*Clinical features of rickets

Answer 4

craniotabes(ping pong sensation of head)

Frontal bossing

rachitic rosary
The costochondral junctions palpable

widened wrists crawlers 
Wide ankles(walkers) 

Harrison sulcus horizontal depression on the lower chest where softened ribs attatch

Bowing of legs from weight bearing

Question 5

*Diagnosis of rickets

Answer 5

• Dietary history (prolonged breastfeeding).

• Blood tests – serum calcium is low or normal,
phosphorus low, plasma alkaline phosphatase activity high, 25-hydroxyvitamin D may be low, and parathyroid hormone elevated.

• X-ray of the wrist joint – shows cupping and fraying of the metaphyses and a widened epiphyseal plate.

Question 6

*Treatment of rickets

Answer 6

balanced diet,
correction of predisposing risk factors, daily administration of vitamin D3 (chole- calciferol).
single oral high dose of vitamin D3 if compliance is poor

Foods rich in vitamin D include eggs, fish, margarine