Vitamin D is a fat-soluble vitamin that also acts as a pleiotropic hormone. There are two major forms of nutritional vitamin D, vitamin D2and D3.
Vitamin D undergoes sequential hydroxylations, and reaches its final active form, 1,25-dihydroxyvitamin D [1,25(OH)2D]. 1,25(OH)2D interacts with its nuclear receptor to modulate gene expression and biological actions.
The vitamin D receptor (VDR) is present in a wide variety of cells including enterocytes, osteoblasts, and renal tubular cells.
Vitamin D is crucial for proper functions of a wide variety of organ systems, and its deficiency is highly prevalent in the general population and also among kidney stone formers.
