This assay is used for the quantitative determination of total 25-hydroxyvitamin D in human serum, plasma, and whole blood, aiding in the assessment of vitamin D sufficiency. Vitamin D, primarily produced in the skin through sunlight exposure, is biologically inactive until hydroxylated in the liver and kidneys to form its active form. Most circulating 25-hydroxyvitamin D is D3, while D2 is measurable mainly in those taking supplements. Vitamin D is crucial for bone health, muscle function, and calcium absorption. Deficiency can lead to rickets, osteomalacia, muscle weakness, and increased fracture risk, particularly in the elderly. It is also associated with secondary hyperparathyroidism and has been linked to various diseases including diabetes, cardiovascular conditions, and immune disorders. Common testing methods include ELISA, chemiluminescence, and immunofluorescence.
