*3.3.1 Intestine*

*Vitamin D Deficiency*

**80**

**Figure 3.**

**Figure 2.**

*Sources, sites, and processing of vitamin D metabolites [10].*

*Calcitriol, 1,25 (OH)2 D3, synthesis and actions with parathyroid hormone (PTH) [8].*

Increasing calcium and phosphorus absorption is the major role of calcitriol in the intestines. It works by the participation of calcitriol with cell membrane receptors to improve calcium absorption [8].
