Answer to Question N-03 about Hypervitaminosis D
MACFitnessOnline.com wrote an interesting post today on
Here’s a quick excerpt
Answer to Biochemistry Question N-03 : ( c ) Vitamin D
Vitamin D is synthesized from a derivative of cholesterol, the 7 dehydrocholesterol. By the action of hv light (290-315 nm) in the skin, it becomes cholecalciferol or Vitamin D3 (inactive).
Cholecalciferol is hydroxylated in the liver by 25 hydroxylase, and in the kidney by a 1 hydroxylase, becoming 1,25 dihydroxycholecalciferol or calcitriol, the active form of vitamin D3.
Vitamin D participates in the regulation of multiple processes, being the more obvious the regulation, together with Parathormone, of Ca++ homeostasis, regulating Ca++ in blood and the balance between Ca++ deposition and Ca++ mobilization from bone.
Hypocalcemia stimulates releasing of PTH, that through cAMP activates 1 hydroxylase in the conversion of VitD to calcitriol.
Calcitriol interacts with a vitamin D receptor (VDR) and initiates a cascade of molecular changes that stimulates the transcription of specific genes, including the synthesis of an intestinal Ca++ binding […]
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