a simple way to understand the D.

1. VITAMIN D
IS THAT SIMPLE?

2. VITAMIN D
Comprises of
• Ergocalciferol (Calciferol, vitamin D2)
• Colecalciferol (Vitamin D3)
• Dihydrotachysterol
• Alfacalcidol (1α – hydroxycholecalciferol)
• Calcitriol (1,25 – dihydroxycholecalciferol)
• Paricalcitol (synethetic analogue)
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3. The Process
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4. D2 and D3
D2 – synthesized in the skin under
the influence of UV rays
D3 – present in irradiated food –
yeasts, fungi, bread, milk, etc.
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5. ACTIONS
• Calcitriol enhances absorption of
calcium & phosphates from
intestine.
• Calcitriol enhances resorption
of calcium and phosphates from
bone.
• Calcitriol enhances tubular
reabsorption of calcium and
phosphate in the kidney.
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6. THE D DEFICIENCY
Plasma calcium and phosphate tend
to fall due to inadequate intestinal
absorption.
As a consequence, PTH (parathyroid
hormone) is secreted calcium
is mobilized from bone in order to
restore plasma Ca2+.
The bone fails to mineralize normally
in the newly laid area, becomes
soft rickets in children and
osteomalacia in adults.
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7. HYPERVITAMINOSIS D
Due to chronic ingestion of large
doses(50,000IU/day) or due to increased
sensitivity of tissues to Vit-D.
Manifestations are due to elevated plasma
calcium and its ectopic deposition.
Hypercalcemia, weakness, fatigue,
vomiting, diarrhea, sluggishness, polyuria,
albuminuria, ectopic Ca2+ deposition(in soft
tissues, blood vessels, parenchymal
organs), renal stones or nephrocalcinosis,
hypertension, growth retardation in
children.
Treatment: withholding the vitamin, low
calcium diet, plenty of fluids &
corticosteroids.
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8. THE KINETICS
Absorbed well from the intestines in the presence
of bile salts, mainly through lymphatics.
Absorption of the D3 form is somewhat better
than that of D2.
In the circulation, it is bound to specific α
globulin & is stored in the body, mostly in
adipose tissues, for many months. It is
hydroxylated in the liver to active & inactive
metabolites. Calcitriol is cleared rapidly.
Metabolites of Vit D are excreted mainly in bile.
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9. THE USES
o Prophylaxis & treatment of nutritional Vit
D deficiencies.
o Metabolic rickets:
• Vit D resistant rickets
• Vit D dependent rickets
• Renal rickets
o Senile or post-menopausal osteoporosis
o Hypoparathyroidism
o Fanconi syndrome (to raise the lowered
phosphate levels)
o Plaque type psoriasis (Ointment form of
Calcipotriol – nonhypercalcemic analogue
of Vit D)
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10. THANK YOU
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