1. Vitamin D3
Presented by John Lear

2. Vitamin D3: The Basics A fat-soluble vitamin: C27H44O
Sources: Skin, Diet
Active form: Calcitriol - steroid hormone
Overall effect: ↑Ca2+ in blood
Vitamin D2: from plants, not as efficient

3. Cholesterol Precursor (in skin)
Structure
Cholesterol Precursor (in skin)

4. (prohormone)
Calcitriol
1,25(OH)2D3

5. Vitamin D3
Pathway

6. Vitamin D Binding Protein

7. Vitamin D Receptor (VDR)
A type of
“Nuclear Receptor”

8. Vitamin D Receptor (VDR)

9. Effects of ↑Calcitriol? (Hint: ↑Ca2+!)
Intestines
↑Absorption of Ca2+ (↑calbindin)
↑Absorption of PO4-
↑Absorption of Mg2+
Parathyroid Glands
↓PTH Synthesis
↓PTH Secretion
3. Bone
↑Ca2+ Resorption from bone
4. Kidneys
↑Ca2+ Reabsorption in tubules
Auto-regulation (negative feedback) of Calcitriol production

10. Regulation of Calcitriol

14. “Permissive Effect”

15. ↓Phosphorus - -
↑Phosphorus +

16. Vitamin D Abnormalities
Normal Blood Vitamin D levels: ng/ml
Vitamin D Abnormalities
Vitamin D Deficiency
Rickets (children)
Osteomalacia (adults)
Secondary Hyperparathyroidism
May lead to:
Depression
Greater risk of cancers

17. Vitamin D Abnormalities
Normal Blood Vitamin D levels: ng/ml
Vitamin D Abnormalities
Vitamin D Toxicity
Calcium Kidney Stones
Bone Pains
Gastrointestinal Pains
Psychological problems

18. In Summation Vitamin D3 Active form is Calcitriol
Primary action: increase intestinal Ca2+ absorption
Closely linked with PTH for Ca2+ and PO4- regulation

19. Thank you!
Sources:
(Dr. David Cohen - Medical Education)