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Vitamin - D
(antirachitic vitamin)
BY
R.PARTHSARATHY

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Introduction
 Vitamin D is a steroid.
 It is present in animals, plants and yeast.
 Insoluble in water, soluble in fat and organic
solutions.
 Sensitive to oxygen, light and iodine.
 Heating and mild acidity can convert into inactive
form.

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Chemical structure
MOST IMPORTANT FORM
It is considered as
prohormone.
BECAUSE
From which
1,25-dehydrocholesterol
synthesized. (active form)

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Metabolism

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Sources
 Liver and viscera of fish.
 Liver of animals which feeds on fish.
 Eggs, butter and milk.
 But the cheapest is the sunlight.

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Functions
 Vitamin D acts on organs such as bone, kidneys, intestinal
mucosa for regulation of calcium and phosphorus metabolism.
 It promotes intestinal absorption of calcium and phosphorus.
 It promotes bone resorption and calcium mobilization to
increase the levels of calcium and phosphorus.(PTH)
 Mineralization of bone is promoted by 1,25-dihydroxy D3.
 It is necessary for the development of bones and normal
growth of the body.
 It also increases the citrate level of blood, bone, kidneys and
heart tissues.

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Functions

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Daily requirements
 Children and infants : 400IU/day
 Adults : 200IU/day
 Plasma concentration of 25-OH D3
Average 25-30 ng/mL
Range 8 - 60 ng/mL
Levels < 10 ng/mL indicative of deficiency
Levels > 150 ng/mL associated with toxicity

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Deficiency manifestations
 Deficiency of vitamin D produces rickets in growing children
with characteristic defects in bone growth.
 Deficiency of vitamin D in adults is called osteomalacia which
is characterized by
- poor intestinal absorption of calcium and phosphorus.
- rise in urinary phosphorous.
- negative calcium balance.
- muscular weakness and early fracture of bone.
- loss of calcium and bowed legs.

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Deficiency manifestations
Pigeon’s chest
Bowed legs

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Toxicity
 Vitamin D is fat soluble, and accumulation (from diet) in
the body can be toxic.
 The long-term safe dose of vitamin D is not known,
however, 10,000 IU /day is safe in healthy adults
 All known cases of vitamin D toxicity have involved
intake of or over 40,000 IU/day.
 The LD50 in man is unknown – there are no reported
deaths from acute toxicity.

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Hyper-vitaminosis
 Excess of vitamin D causes toxicity characterized by
Nausea
Anorexia
Digestive disturbances and calculi formation.
Elfin facies

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Factors that influence
vitamin D status
 Genetics
 Vitamin D resistant rickets (hypophosphatemic rickets)
 Vitamin D dependent rickets (type I)
 Vitamin D dependent rickets (type II)
 Drugs
Anticonvulsant drugs such as Diphenylhydatoin, phenobarbital
 Alcohol
 low 25(OH)D level
 Age
 Low epidermal con of 7-dehydrocholesterol
 1-hydroxylase: less responsive to PTH
 Sex

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Thank you