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The conversion of vitamin D, especially cholecalciferol, to 25(OH)D (calcifediol) is one of the key steps in the vitamin D hormonal system. The CYP2R1 enzymatic activity achieving this process was previously thought to be constitutively expressed and stable, so that serum 25(OH)D was a measure of the supply of vitamin D. [9]
Calcitriol is a hormone and the active form of vitamin D, normally made in the kidney. [ 8 ] [ 9 ] [ 10 ] It is also known as 1,25-dihydroxycholecalciferol . It binds to and activates the vitamin D receptor in the nucleus of the cell, which then increases the expression of many genes. [ 11 ]
The conversion of calcifediol to calcitriol is catalyzed by the enzyme 25-hydroxyvitamin D 3 1-alpha-hydroxylase, which is the product of the CYP27B1 human gene. The activity of CYP27B1 is increased by parathyroid hormone and also by low plasma calcium or phosphate. [ 1 ]
Hormones predominate at the left part of the scale, shown with a red at ng/L or pmol/L, being in very low concentration. There appears to be the greatest cluster of substances in the yellow part (μg/L or nmol/L), becoming sparser in the green part (mg/L or μmol/L).
Mapping of several bone diseases onto levels of vitamin D (calcidiol) in the blood [6] Normal bone vs. osteoporosis. Vitamin D deficiency is typically diagnosed by measuring the concentration of the 25-hydroxyvitamin D in the blood, which is the most accurate measure of stores of vitamin D in the body.
A broad reference range of 20 to 150 nmol/L (8-60 ng/mL) has also been suggested, [16] while other studies have defined levels below 80 nmol/L (32 ng/mL) as indicative of vitamin D deficiency. [ 17 ] Increasing calcifediol levels up to levels of 80 nmol/L (32 ng/mL) are associated with increasing the fraction of calcium that is absorbed from ...
Ergocalciferol, also known as vitamin D 2 and nonspecifically calciferol, is a type of vitamin D found in food. It is used as a dietary supplement [3] to prevent and treat vitamin D deficiency [4] due to poor absorption by the intestines or liver disease. [5]
It is then converted in the liver to calcifediol (25-hydroxycholecalciferol D), which is further converted in the kidney to calcitriol (1,25-dihydroxycholecalciferol D). [4] One of calcitriol’s most important functions is to promote calcium uptake by the intestines. [5] Cholecalciferol is present in food such as fatty fish, beef liver, eggs ...