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proteins. 25-Hydroxyvitamin D 1-alpha-hydroxylase (VD 1A hydroxylase) also known as calcidiol 1-monooxygenase[ 5 ] or cytochrome p450 27B1 (CYP27B1) or simply 1-alpha-hydroxylase is a cytochrome P450 enzyme that in humans is encoded by the CYP27B1 gene. [ 6 ][ 7 ][ 8 ] VD 1A hydroxylase is located in the proximal tubule of the kidney and a ...
Vitamin D activation occurs in the kidney. PTH up-regulates 25-hydroxyvitamin D 3 1-alpha-hydroxylase, the enzyme responsible for 1-alpha hydroxylation of 25-hydroxy vitamin D, converting vitamin D to its active form (1,25-dihydroxy vitamin D).
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]
Calcifediol, also known as calcidiol, 25-hydroxycholecalciferol, or 25-hydroxyvitamin D3 (abbreviated 25 (OH)D3), [1] is a form of vitamin D produced in the liver by hydroxylation of vitamin D 3 (cholecalciferol) by the enzyme vitamin D 25-hydroxylase. [3][4][5] Calcifediol can be further hydroxylated by the enzyme 25 (OH)D-1α-hydroxylase ...
A diet insufficient in vitamin D, combined with inadequate sunlight exposure, can lead to vitamin D deficiency, which is defined as a blood 25-hydroxyvitamin D or 25(OH)D level below 12 ng/mL (30 nmol/liter). Vitamin D insufficiency, on the other hand, is characterized by a blood 25(OH)D level between 12–20 ng/mL (30–50 nmol/liter).
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. [1][7][2] One nanogram per millilitre (1 ng/mL) is equivalent to 2.5 nanomoles per litre (2.5 nmol/L). Severe deficiency: <12 ng/mL = <30 nmol/L[2] Deficiency ...
CYP2R1 is cytochrome P450 2R1, an enzyme which is the principal vitamin D 25-hydroxylase. [5] [6] In humans it is encoded by the CYP2R1 gene located on chromosome 11p15.2. [7]It is expressed in the endoplasmic reticulum in liver, where it performs the first step in the activation of vitamin D by catalyzing the formation of 25-hydroxyvitamin D. [8]
Extended Release Calcifediol was recently approved by the FDA as a treatment for secondary hyperparathyroidism (SHPT) in adults with stage 3 or 4 chronic kidney disease (CKD) and low vitamin D blood levels (25-hydroxyvitamin D less than 30 ng/mL). It can help treat SHPT by increasing Vitamin D levels and lowering parathyroid hormone or PTH.