Bone loss refers to a decline in bone mass per unit volume of bone and is a sign of early osteoporosis, which can occur with continued aggravation. It occurs mostly in perimenopausal women, the elderly, and people who lack exercise, and can increase the risk of fracture. There are several causes of bone loss: 1. Menopause. After menopause, estrogen secretion in women decreases significantly, leading to active osteoclast function, causing bone loss and bone loss. 2. Aging. Aging will lead to a decline in sex hormones, increasing osteoclast activity and reducing osteoblast activity, while the combined effects of nutrient absorption and reduced exercise lead to a decline in bone mass. 3, secondary diseases. For example, hyperthyroidism, hyperparathyroidism, etc. 4, bad habits, such as smoking, heavy alcohol consumption, lack of exercise, partial diet and calcium deficiency or vitamin D deficiency, etc.