VDR and Hypocalcemia: Our findings showed that prednisolone administration led to a decrease in the level of 25-dihydroxyvitamin D, a vitamin D status marker, in the serum along with an impaired bone synthesis of key components of the vitamin D auto-/paracrine system, VDR and CYP27B1, and consequently induced hypophosphatemia and hypocalcaemia and increased the activity of alkaline phosphatase in the serum and reduced content of mineral components in bone tissue.