文档介绍：儿科医院
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Vitamin D deficiency
Provitamin D3
Ultraviolet light
In the skin:
7-dehydrocholesterol
Vitamin D3
(an inactive form)
25-hydroxy vitamin D3
Hydroxylation
In the Liver:
foods
1, 25-hydroxy vitamin D3
(active form)
Hydroxylation
In the kidneys:
Vitamin D Synthesis and Activation
Vitamin D roles
Facilitate intestinal absorption of calcium and phosphorus
Promote renal reabsorption of phosphorus
Direct effect on bone deposition and reabsorption of calcium and phosphorus
Maintain calcium and phosphorus homeostasis
Ca, P
Homeostasis
+1,25(OH)2D
+PTH
-CT
+1,25(OH)2D
-PTH
-CT
+1,25(OH)2D
Bone
Intestine
Kidneys
Parathormone
(PTH)
Calcitonin
(CT)
1,25(OH)2D
Ca, P
Homeostasis
Causes of Vitamin D deficiency
Inadequate direct exposure to sunlight
Inadequate vitamin D intake
Higher requirement
Some diseases, which interfere with vitamin D absorption or metabolic and activation
Vitamin D-Deficient Rickets
Epidemiology:
rare in industrialized countries
Common in China
20% in the South of China
30-40% in the North of China
Vitamin D deficiency
Osteoid tissue failure to mineralize
Osteoid tissue accumulation
Less Ca absorbed from the intestine
Urine phosphorus increased
Parathormone secreted
Serum AKP increased
Mobilized bone Ca,P
Vitamin D-deficient
Rickets
Serum Ca concentration decrease
Low serum phosphorus
Pathophysiology of Vitamin D-deficient Rickets
Normal or slight decrease in serum calcium concentration
General manifestations: irritability, temporary
teeth eruption delayed,anterior fontanel
closure delayed
Muscles lack of tone
Head: craniotabes, Ping-Pong ball,caput quadratum
Chest: beading of the ribs,
pigeon breast deformity, Harrison groove
Limb: Thickening of the wrists and ankles
Bow-legs, knock-knees
Cliniacl manifestations
Caput quadratum
Pigeon breast deformity