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Serum level of 25(OH)D is the laboratory test ordered to indicate whether or not a person has vitamin D deficiency or insufficiency. [53] It is also considered reasonable to treat at-risk persons with vitamin D supplementation without checking the level of 25(OH)D in the serum, as vitamin D toxicity has only been rarely reported to occur.
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]
Vitamin D toxicity, or hypervitaminosis D, is the toxic state of an excess of vitamin D.The normal range for blood concentration of 25-hydroxyvitamin D in adults is 20 to 50 nanograms per milliliter (ng/mL).
The name 25(OH)D refers to any combination of calcifediol (25-hydroxy-cholecalciferol), derived from vitamin D 3, and ercalcidiol (25-hydroxy-ergocalciferol), [1] derived from vitamin D 2. The first of these (also known as 25-hydroxy vitamin D3) is made by the body, or is sourced from certain animal foods or cholecalciferol supplements. The ...
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). [216] This form of vitamin D is the active hormone which promotes calcium uptake from the intestine via the action of calbindin. [218] Calcitriol also reduces calcium loss to urine. [215]
Reference ranges (reference intervals) for blood tests are sets of values used by a health professional to interpret a set of medical test results from blood samples. Reference ranges for blood tests are studied within the field of clinical chemistry (also known as "clinical biochemistry", "chemical pathology" or "pure blood chemistry"), the ...
CYP24A1 appears to be "a multicatalytic enzyme catalyzing most, if not all, of the reactions in the C-24/C-23 pathway of 25-OH-D 3 metabolism." [5] It has been proposed that 24,25-dihydroxyvitamin D 3 is a metabolite of 25-hydroxyvitamin D 3 which is destined for excretion. [5]
The Institute of Medicine in 2010 recommended a maximum uptake of vitamin D of 4000 IU/d, finding that the dose for lowest observed adverse effect level is 40,000 IU daily for at least 12 weeks, [25] and that there was a single case of toxicity above 10 000 IU after more than seven years of daily intake; this case of toxicity occurred in ...