125OH2D2

125OH2D2 is a less common metabolite of vitamin D, specifically calcifediol (25-hydroxyvitamin D). While 25-hydroxyvitamin D is the primary circulating form of vitamin D and is often measured to assess vitamin D status, 125OH2D2 represents a further hydroxylation of this molecule. The most biologically active form of vitamin D is calcitriol (1,25-dihydroxyvitamin D), which is produced by the kidneys. The designation "2D2" refers to the specific dihydroxylation occurring at the second carbon of the vitamin D molecule, leading to 1,25-dihydroxyvitamin D2. However, it is important to distinguish this from 1,25-dihydroxyvitamin D3, which is derived from vitamin D3. Vitamin D2 is primarily obtained from plant-based sources and fortified foods, whereas vitamin D3 is synthesized in the skin upon sun exposure and found in animal products. The production and physiological roles of 125OH2D2 are less well-understood compared to its D3 counterpart. Research into the specific functions and significance of 125OH2D2 in human health is ongoing. Its concentration in the body is generally much lower than that of 25-hydroxyvitamin D.