**1. Introduction**

According to WHO technical report in 1994, osteoporosis is a disease characterized by low bone mass and microarchitectural deterioration of bone tissue leading to enhanced bone fragility, and consequently increases the fracture risk. Since fracture does not solely depend on bone mass, osteoporosis was defined by NIH as a skeletal disorder, characterized by compromised bone strength predisposing to an increased risk of fracture. Although aging is a major risk for fracture, it is a strong risk for chronic kidney disease (CKD) as well. Thus, patients having comorbidity of CKD and osteoporosis are sometimes found. According to a study NHANES III (the Third National Health and Nutrition Examination Survey, 1988-1994) in the US, in women with osteoporosis, 85% (95%CI: 79-91%) showed Creatinine clearance (Ccr)≤60mL/min and 24% (95%CI: 19-29%) were of Ccr<35mL/min [1]. Another study dem‐ onstrated that Ccr≤60mL/min is an independent risk factor for fracture at vertebra, femur and radius [2].

In addition to aging, a female sex, low bone mineral density (BMD), prevalent fracture, family history of fracture and lower body weight, life style such as drinking, smoking and excise and common diseases would affect risk for fracture [3, 4]. Recent studies demonstrate that measurement of BMD by Dual-energy X-ray absorptiometry (DXA), which is a gold standard for diagnosis of osteoporosis, is less useful for the fracture prediction in the patients with diabetes mellitus and the patients under glucocorticoid therapy [5-8]. Among these popula‐ tion, BMD-independent bone fragility and falls may be involved in an elevation of the risk for fracture. Therefore, much interest is focused on the link between kidney dysfunction /CKD and fracture /osteoporosis [9].

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