VITAMIN D   

              

.The general term "vitamin D" refers to a collection of chemically connected substances with antirachitic properties. Vitamin D2 (ergocalciferol) and Vitamin D3 are the two most well-known members of this category (cholecalciferol).

 VITAMIN D2 & D3

From the 1940s to the 1960s, foods were fortified with vitamin D in the form of vitamin D2, which is generated from the common plant steroid ergosterol. When the sun's radiant energy contacts the skin and transforms the precursor 7-dehydrocholesterol, vitamin D3 is produced. Since vitamin D3 may be produced by the body, it does not fit the traditional definition of a vitamin. Along with calcitonin and parathyroid hormone, vitamin D helps to maintain calcium homeostasis in the body (PTH). Additionally, crucial vitamin D is also important for phosphorus homeostasis

CALCIUM 

Calcium and phosphorus are required for a wide variety of biological processes. Calcium is necessary for muscle contraction, nerve pulse transmission, blood clotting, and membrane structure. It also serves as a cofactor for such enzymes as lipases and ATPases and is needed for eggshell formation in birds. It is an important intracellular signaling molecule for signal transduction pathways such as those involving calmodulin and protein kinase C (PKC).

PHOSPHORUS

Phosphorus is an important component of DNA, RNA, membrane lipids, and the intracellular energy-transferring ATP system. The phosphorylation of proteins is important for the regulation of many metabolic pathways. The maintenance of serum calcium and phosphorus levels within narrow limits is important for normal bone mineralization.

 The active form of vitamin D3, 1a,25(OH)2D3, has been shown to act on novel target tissues not related to calcium homeostasis. There have been reports characterizing receptors for the hormonal form of vitamin D and activities in such diverse tissues the as brain, pancreas, pituitary, hair follicle, skin, muscle, immune cells, and parathyroid. These studies suggest that vitamin D status is important for insulin and prolactin secretion, hair growth, muscle function, immune and stress response melanin synthesis, and cellular differentiation.