Patients with chronic renal insufficiency usually develop secondary osteoporosis or bone loss, which is called renal osteodystrophy. Most of the previous studies focused on bone metabolism of patients in late stage of chronic renal insufficiency, especially those with chronic dialysis. In this study, bone metabolism of patients in different stages of chronic renal insufficiency will be observed to reveal the mechanism of development of renal osteodystrophy and provide clues for early intervention on renal osteodystrophy.