PTH and osteoporosis: In this study, we examined the 1) efficacy of denosumab therapy, and 2) the transitions in serum calcium, phosphorus, 1,25(OH)2D3, and parathyroid hormone (PTH), which plays important roles in determining bone resorption and bone mass, with or without vitamin D and calcium supplementation over a period of four years in primary Japanese osteoporosis patients.