Traditional risk factors, such as smoking, aging, and a variety of factors associated with COPD disease itself, can contribute to osteoporosis. In the case of COPD disease itself, systemic inflammatory response, hypoxemia and indirectly vitamin D deficiency, reduced exercise, and low BMI are risk factors, while patients with COPD tend to be older and on long-term glucocorticoid therapy, making them more exposed to the risk of osteoporosis. Under normal conditions, bone tissue is in a constant state of renewal, with bone resorption by osteoclasts and bone formation by osteoblasts alternating to maintain a balance in bone mass. This process of bone metabolism depends mainly on the levels of parathyroid hormone (PTH), vitamin D and sex hormones in the body, and is a complex process of interaction between osteoblasts, osteoclasts and osteocytes. The relationship is close. 1, systemic inflammatory response: The main lesion of chronic obstructive pulmonary disease is characterized by systemic inflammatory response, and inflammatory cells release a series of inflammatory mediators and cytokines. Inflammatory mediators directly or indirectly stimulate the proliferation and differentiation of osteoclasts, thus affecting bone metabolism. 2, hypoxemia: Patients with chronic obstructive pulmonary disease have reduced pulmonary ventilation, diffusion function and dysregulation of the ratio of ventilation and blood flow, resulting in different degrees of hypoxemia. Long-term chronic hypoxia can lead to a series of pathological changes in tissue structure and function of various systems causing metabolic disorders. Reduced partial pressure of oxygen may indirectly cause osteoporosis by aggravating dyspnea in patients with chronic obstructive pulmonary disease, which in turn reduces their exercise. Hypoxia can stimulate osteoclastogenesis, promote osteoclastic differentiation and promote bone loss. 3.Low body mass index (BMI): Nutritional status is an important determinant of clinical symptoms and prognosis of COPD patients, and BMI is widely used to assess the nutritional status of the body. COPD patients with poorer nutritional status are more likely to suffer from osteoporosis, mainly associated with poor dietary intake due to infection, gastrointestinal hypoxia, and increased oxygen consumption catabolism. Regression analysis showed that lower BMI was an independent risk factor for secondary osteoporosis in patients with COPD. Vitamin D deficiency: Low levels of vitamin D can stimulate the secretion of PTH and increase the blood calcium level of the body. Also lower levels of vitamin D can induce the production of osteoclasts. In addition, studies have shown that 1,25(OH)2D3 can also induce the expression of OPG in osteoblasts and inhibit the production of osteoclasts. 5.Decreased secretion of sex hormones: Estrogen has the functions of inhibiting bone resorption, enhancing osteoblast activity, inhibiting osteocalcinolysis and promoting bone reconstruction. Androgens have the role of promoting protein synthesis and bone matrix synthesis in elderly patients with chronic obstructive pulmonary disease, especially those who apply glucocorticoids, are more prone to osteoporosis due to hypogonadism and reduced production of estrogen and androgens. 6, smoking: smoking as an important pathogenic factor of COPD, and a higher incidence of fracture. A meta-analysis of the effects of smoking on bone density found that smoking had a negative effect on bone density at major osteoporosis-related fracture occurrences, such as the hip, vertebrae, and forelimbs. 7, glucocorticoid application: long-term inhalation of glucocorticoids can effectively reduce the inflammatory response in the stable phase of chronic obstructive pulmonary disease and reduce patient mortality, but long-term systemic application of glucocorticoids can cause osteoporosis. Studies have confirmed that glucocorticoids affect bone metabolism through a variety of mechanisms. In addition, glucocorticoids can increase osteoclast activity, inhibit osteoblast proliferation, promote bone resorption and decrease bone reconstruction.