GC-induced 25(OH)D deficiency and abnormalities in vitamin D metabolism caused a decrease in the synthesis of osteoclastic marker RANK and affected angiogenesis/osteogenesis coupling (reduced VEGF-A levels) that, in general, resulted in osteoporosis and deterioration of the basic biomechanical parameters of rat femurs. This evidence concerns the gene TNFRSF11A and osteoporosis.