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Multivitamins nutrition facts label showing that the international unit of, for example, vitamins D and E correspond to different gram values. In pharmacology, the international unit (IU) is a unit of measurement for the effect or biological activity of a substance, for the purpose of easier comparison across similar forms of substances.
A third important effect of PTH on the kidneys is stimulation of the conversion of 25-hydroxy vitamin D into 1,25-dihydroxy vitamin D (calcitriol). [221] This form of vitamin D is the active hormone which promotes calcium uptake from the intestine via the action of calbindin. [223] Calcitriol also reduces calcium loss to urine. [220]
Cholecalciferol is a form of vitamin D which is naturally synthesized in skin and functions as a pro-hormone, being converted to calcitriol. This is important for maintaining calcium levels and promoting bone health and development. [4] As a medication, cholecalciferol may be taken as a dietary supplement to prevent or to treat vitamin D ...
1α-Hydroxyvitamin D 5 is a chemical derivative of vitamin D 5.The motive to study 1α-hydroxyvitamin D 5 as a potential pharmaceutical drug stemmed from the tendency of calcitriol, a natural metabolite produced in the kidney, to cause toxic hypercalcemia in patients when dosed at concentrations needed to interrupt prostate cancer cells' cycle and stimulate apoptosis.
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]
22-Dihydroergocalciferol is a form of vitamin D, also known as vitamin D 4. [2] It has the systematic name (5Z,7E)-(3S)-9,10-seco-5,7,10(19)-ergostatrien-3-ol. [1]
The katal (symbol: kat) is that catalytic activity that will raise the rate of conversion by one mole per second in a specified assay system. [1] It is a unit of the International System of Units (SI) [1] used for quantifying the catalytic activity of enzymes (that is, measuring the enzymatic activity level in enzyme catalysis) and other catalysts.
The natural, active form of vitamin D is calcitriol (1,25-dihydroxycholecalciferol). This molecule and other naturally occurring forms of vitamin D, including its precursors and metabolites, have been modified to synthesize pharmaceuticals with potentially greater, or selective, therapeutic actions. [1] [2] [3] [4]