Pharmacology of Vitamin D

Vitamin D3 is formed in the skin, converted to a pre-hormone in the liver and becomes a fully active hormone in the kidney

Vitamin D3 (cholecalciferol) is formed in the skin by a photoreaction between ultraviolet (UV) rays of sunlight and a pre-cholesterol compound (7-dehydrocholesterol) in the skin.  Vitamin D3 is inert, that means it is not bioactive.  Vitamin D3 is also unstable, especially in the presence of air or oxygen. 

Cool Vitamin D Pharmacology Vitamin D hormone synthesis

As shown in the figure above, Vitamin D3 is transported in the blood stream to the liver where it is converted into the pre-hormone form, 25-hydroxy Vitamin D3 by the enzymatic addition of a single hydroxyl [OH-] group.  This pre-hormone form is also largely inert and unstable in the presence of air or oxygen.  This pre-hormone form is also called calcidiol.

The pre-hormone form of Vitamin D3 is then transported from the liver to the kidneys where it is converted to the active hormone form, 1, 25-dihydroxy Vitamin D3 by the enzymatic addition of a second hydroxyl [OH-] group.  The hormone form of Vitamin D3 is highly bioactive and also unstable in the presence of air or oxygen.  This hormone form is also called calcitriol.

  • Cellular and Immune Functions
    The active hormone binds into the Vitamin D receptor (VDR) that is an essential component to most cellular and immune functions.
  • Vitamin D Associated Diseases
    Vitamin D deficiencies can cause or contribute to diseases such as colorectal and prostate cancers, high blood pressure, and kidney and heart diseases, which affect black Americans at higher rates than whites.  


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