Call

Calcium absorption requires assistance from Vitamin D. The active form of Vitamin D is known as $1,25$-Dihydroxy Cholecalciferol or Calcitriol.

Now,skin contains a precursor of this thing known as $7$-Dehydrocholesterol(Pre-cholecalciferol),which undergoes non enzymatic reaction due to UV ray of Sun light.

Now this Pre-cholecalciferol undergoes thermal isomerization over hours to form Cholecalciferol(Vitamin D),that gets absorbed to blood stream.

This Cholecalciferol is hydroxylated in liver to form $25$-Hydroxy-cholecalciferol. This thing when released again in to the circulation,binds to a specific type of globulin,which acts as main storage of Vitamin D.

After this thing comes to kidney it undergoes another hydroxylation,which can be of two types,one is forming of $1,25$-Dihydroxycholecalciferol or Calcitriol. This helps in calcium absorption.

Or,it can make $24,25$-Dihydroxycholecalciferol which is an inactive metabolite of Vitamin D

Talk Doctor Online in Bissoy App