From a biochemical point of view, osteomalacia caused by vitamin D deficiency evolves in three stages: an initial stage characterized by normal serum levels of calcium and phosphate and elevated levels of alkaline phosphatase, serum PTH, and 1,25‐dihydroxyvitamin D [1,25(OH)2D]—the latter as a consequence of increased PTH. This evidence concerns the gene PTH and osteomalacia.