Changes

#GI tract - indirect effects occur via activation of Vitamin D3.

#GI tract - indirect effects occur via activation of Vitamin D3.

===Calcitriol (Active Vitamin D3)===

===Calcitriol (Activated Vitamin D3)===

 

'''Calcitriol''', or '''1,25-dihydroxycholecalciferol''' is the biologically active metabolite of vitamin D. It is classified as a steroid hormone and acts to raise blood calcium levels.

'''Calcitriol''', or '''1,25-dihydroxycholecalciferol''' is the biologically active metabolite of vitamin D.

It is classified as a steroid hormone and acts to raise the blood calcium level.

There are two dietary sources of Vitamin D3 -  

There are two dietary sources of Vitamin D3 -  

*'''Vitamin D2''' produced in plants (ergocalciferol) (lower activity that D3)

#'''Vitamin D2''' is produced in plants (ergocalciferol) (lower activity that D3 by the action of UV light

**This is produced by the action of UV light

#'''Vitamin D3''' produced in animals (cholecalciferol) from cholesterol within membranes, and is fat soluble.

*'''Vitamin D3''' produced in animals (cholecalciferol)

**This is produced from cholesterol within membranes, and is fat soluble.

Vitamin D can also be converted from 7-dehydrocholesterol by Ultraviolet radiation at wavelength 300nm in the [[Skin - Anatomy & Physiology|skin]]. This is not a major source in animals as the majority of the skin is covered by hair.

Vitamin D can also be converted from 7-dehydrocholesterol by ultraviolet radiation at wavelength 300nm in the [[Skin - Anatomy & Physiology|skin]]. This is not a major source in animals as the majority of the skin is covered by hair.

====Active Vitamin D Synthesis====

====Active Vitamin D Synthesis====