Secalciferol ((24R)-24,25-Dihydroxyvitamin D3) is the major active metabolite of Vitamin D. Secalciferol activates vitamin D receptor (VDR) with an EC50 value of 150 nM. Secalciferol is involved in a wide range of biological functions such as calcium homeostasis, cellular differentiation and proliferation processes, as well as other functions related to the immune system, which is promising for research of rickets, osteomalacia, hypercalcemia and autoimmune disorders.