Activation of inactive Vitamin D requires two hydroxylation processes. The first hydroxylation process occurs in the liver. During this process, the inactive vitamin D is hydroxylated at carbon 25 (C-25) by 25 hydroxylases (25OHase). This hydroxylation process results in the chemical conversion of Vitamin D to 25 hydroxyvitamin D (25(OH) D), which is the primary form of vitamin D in the circulation system. This property of 25 hydroxyvitamin D makes it …show more content…
This transporting carrier protein is called vitamin D-binding protein (DBP).
The primary function of vitamin D is to maintain calcium and phosphorus homeostasis through three different mechanisms. One of these mechanisms involves increasing intestinal calcium absorption. The homeostatic state is also achieved by moving calcium and phosphorus from a skeletal body part to the blood in order to ensure an optimal blood level. Finally, decreasing renal calcium and phosphorus excretion is also crucial to reach a homeostatic balance of the body. Other functions of vitamin D include cell differentiation, immune system regulation, insulin secretion, and blood pressure control (Holick,