Bone density examination should be performed in the following cases to clarify whether osteoporosis is present: 1. Those who are amenorrheic before the age of 45; 2. Postmenopausal women with a family history of osteoporosis; 3. Those with frequent low back pain, hunchback or shorter height than before; 4. Those with vertebral abnormalities or reduced bone mass found on X-ray, who need to exclude osteoporosis; 5. Those who apply glucocorticoids for a long time (more than 3 months); 6. hyperparathyroidism, hyperthyroidism, diabetes mellitus and liver and kidney diseases that increase the risk of osteoporosis; 7, male hypogonadism; 8, chronic alcohol drinkers; 9, chronic calcium intake; 10, chronic gastrointestinal diseases, such as malabsorption and major gastrectomy for more than 10 years; 11, excessive urinary calcium with or without kidney stones; 12, chronic less active people; 13. Those who suffer from rheumatoid arthritis and ankylosing spondylitis; 14, those who take excessive thyroid hormone, methotrexate and antidepressant drugs for a long time.