Ercalcidiol is a metabolite of vitamin D2 and is a VDR-like receptor [1].Vitamin D is a group of fat-soluble secosteroids and plays an important role in enhancing intestinal absorption of calcium, iron, magnesium, phosphate and zinc. Ercalcidiol (25-hydroxy Vitamin D2) and 25-hydroxyergocalciferol (aka 25-hydroxyvitamin D2 — abbreviated 25(OH) D2) are vitamin D metabolites and Ercalcidiol is converted to 25-hydroxyergocalciferol in liver. Through measuring the level of Ercalcidiol and 25-hydroxyergocalciferol in serum can detect the person’s vitamin D status [2] [3].Using isolated perfused rat kidney model, it was demonstrated that Ercalcidiol not only converted into 24, 25-dihydroxyvitamin D2 but also converted into two other new metabolites-24, 25, 28-trihydroxyvitamin D2 and 24, 25, 26-trihydroxyvitamin D2 [4]. When tested with male weanling rat model, it was demonstrated that either a protein deficiency or a total food restriction during the early postweaning period had no effect on the synthesis and transport of Ercalcidiol and 23, 25-dihydroxyvitamin D in plama [5].References: [1]. Jones, G., H.K. Schnoes, and H.F. DeLuca, An in vitro study of vitamin D2 hydroxylases in the chick. J Biol Chem, 1976. 251(1): p. 24-8.[2]. Newman, M.S., et al., A liquid chromatography/tandem mass spectrometry method for determination of 25-hydroxy vitamin D2 and 25-hydroxy vitamin D3 in dried blood spots: a potential adjunct to diabetes and cardiometabolic risk screening. J Diabetes Sci Technol, 2009. 3(1): p. 156-62.[3]. Thacher, T.D., et al., Comparison of metabolism of vitamins D2 and D3 in children with nutritional rickets. J Bone Miner Res, 2010. 25(9): p. 1988-95.[4]. Reddy GS1, Tserng KY. 24, 25, 28-trihydroxyvitamin D2 and 24, 25, 26-trihydroxyvitamin D2: novel metabolites of vitamin D2.Biochemistry. 1990 Jan 30; 29(4):943-9.[5]. Philbrick DJ, Hollis BW, Draper HH. Effects of protein deficiency on plasma levels of 25-hydroxyvitamin and 24, 25-dihydroxyvitamin D in the rat. Am J Clin Nutr. 1980 Oct;33(10):2174-6.