After middle age, the body tends to be in negative calcium homeostasis. Whenever calcium intake is insufficient, the body’s blood calcium self-stabilization system increases the secretion of parathyroid hormone, which dissolves bone calcium to replenish blood calcium and maintain it at its original level. If the body is chronically deficient in calcium and it is not corrected, the blood calcium stabilization system will be deviated. The parathyroid glands are stimulated by chronic calcium deficiency and continue to secrete excessive amounts of parathyroid hormone, causing the parathyroid glands to enter a hyperactive state, resulting in a paradoxical decrease in bone calcium and an increase in blood calcium and soft tissue calcium levels. High blood calcium stimulates increased calcitonin secretion and promotes osteogenesis, which is the hormonal basis for the coexistence of osteoporosis and osteomalacia. Osteomalacia is just a compensatory effect of the body on osteoporosis. The new bone formed by the body with this compensatory effect is far from being able to make up for the large amount of lost old bone, and the calcium that should enter the interior of the bone is deposited and repaired on some of the most stressed bone surfaces, such as the cervical vertebrae, lumbar vertebrae, and heel bone, etc. This is osteomalacia. Osteoporosis and osteomalacia, which often afflict middle-aged and elderly people at the same time, are a pair of contracted bone diseases caused by the lack of calcium in the body.