Vitamin D as Hormone
VITAMIN D (CALCITRIOL)
INTRODUCTION:
Bioactive vitamin D or calcitriol is a steroid hormone that has long been known for its important role in regulating body levels of calcium and phosphorus, and in mineralization of bone. More recently, it has become clear that receptors for vitamin D are present in a wide variety of cells, and that this hormone has biologic effects which extend far beyond control of mineral metabolism. Vitamin D is thus not a true vitamin, as it can be synthesized in adequate amounts by most mammals exposed to sunlight (cats and dogs cannot synthesize vitamin D and must receive it in their diet). An organic chemical compound (or related set of compounds) is only scientifically called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from their diet. However, as with other compounds commonly called vitamins, vitamin D was discovered in an effort to find the dietry substance that was lacking in a disease, namely, rickets, the childhood form of osteomalacia.
ROLE OF VITAMIN D IN REGULATION OF SEVERAL GENES:
The vitamin D hormones have essential roles in human health. Vitamin D hormones act by binding to and activating the vitamin D receptor (VDR) to regulate the expression of genes in a tissue-specific manner. Vitamin D hormones regulate blood calcium levels by controlling intestinal absorption of dietary calcium and reabsorption of calcium by the kidneys. Concomitantly, vitamin D hormones also suppress the production of the calcium regulating hormone, parathyroid hormone (PTH), which is produced by the parathyroid glands.
The vitamin D hormones also participate in the regulation of cellular differentiation and growth, as well as bone formation and metabolism. Additionally, vitamin D hormones are required for the normal functioning of the musculoskeletal, immune and renin-angiotensin systems. There is a growing body of evidence linking
INTRODUCTION:
Bioactive vitamin D or calcitriol is a steroid hormone that has long been known for its important role in regulating body levels of calcium and phosphorus, and in mineralization of bone. More recently, it has become clear that receptors for vitamin D are present in a wide variety of cells, and that this hormone has biologic effects which extend far beyond control of mineral metabolism. Vitamin D is thus not a true vitamin, as it can be synthesized in adequate amounts by most mammals exposed to sunlight (cats and dogs cannot synthesize vitamin D and must receive it in their diet). An organic chemical compound (or related set of compounds) is only scientifically called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from their diet. However, as with other compounds commonly called vitamins, vitamin D was discovered in an effort to find the dietry substance that was lacking in a disease, namely, rickets, the childhood form of osteomalacia.
ROLE OF VITAMIN D IN REGULATION OF SEVERAL GENES:
The vitamin D hormones have essential roles in human health. Vitamin D hormones act by binding to and activating the vitamin D receptor (VDR) to regulate the expression of genes in a tissue-specific manner. Vitamin D hormones regulate blood calcium levels by controlling intestinal absorption of dietary calcium and reabsorption of calcium by the kidneys. Concomitantly, vitamin D hormones also suppress the production of the calcium regulating hormone, parathyroid hormone (PTH), which is produced by the parathyroid glands.
The vitamin D hormones also participate in the regulation of cellular differentiation and growth, as well as bone formation and metabolism. Additionally, vitamin D hormones are required for the normal functioning of the musculoskeletal, immune and renin-angiotensin systems. There is a growing body of evidence linking