The blood calcium level of osteoporosis patients is not low, so why do they need to supplement calcium?

This is the 4962nd article of Da Yi Xiao Hu

"Osteoporosis" is a common disease that seriously threatens the health of the elderly. It has the characteristics of high morbidity, high disability rate, high mortality rate, high medical expenses and low quality of life (i.e. "four highs and one low"). Many people believe that osteoporosis is caused by calcium deficiency, so they take a lot of calcium supplements, but osteoporosis still occurs. After blood tests, the blood calcium is not low. However, the doctor still asks the patient to supplement calcium, so I am very confused. Why is the blood calcium not low in osteoporosis? If the blood calcium is not low, why do we need to supplement calcium?

Calcium and bones

Calcium is the most abundant inorganic element in the human body and an important and indispensable trace element in the organism. It is both a builder of the body and a regulator of the physiological functions of the human body. 99% of the calcium in the human body is deposited in bones and teeth, promoting their growth and development and maintaining their shape and hardness.

Bones are the largest calcium warehouse in the human body. Most of the calcium in the body is stored in bones, namely bone calcium. Bone metabolism is a slow process. Bone tissue is constantly absorbed and removed by osteoclasts, and osteoblasts form new bone tissue. Bone tissue is through an uninterrupted bone reconstruction process, with new bone replacing old bone to keep bones young.

Why do most people have normal blood calcium levels when they have osteoporosis?

The calcium concentration in the blood is maintained within the normal range through the regulation of a variety of hormones (such as parathyroid hormone, calcitonin, etc.). When blood calcium decreases, the body will increase the activity of osteoclasts through hormone regulation, mobilize calcium in the bones to release into the blood, and maintain normal blood calcium; conversely, when dietary calcium intake is excessive, calcium regulating hormones stimulate osteoblast activity, causing excess blood calcium to be deposited in the bones. Therefore, blood calcium levels are the result of maintaining a dynamic balance of normal physiological needs of the human body. This also explains why many patients have osteoporosis, or even severe osteoporosis, but blood calcium tests are often still normal, but bone calcium is already very deficient at this time.

Since blood calcium does not mean that there is no calcium deficiency, why do we still need to measure blood calcium?

On the one hand, calcium is one of the basic elements of bone synthesis. Osteoporosis means insufficient bone calcium. Supplementing with adequate calcium is beneficial to improving bone quality. On the other hand, many anti-osteoporosis drugs are prone to hypocalcemia during use, so hypocalcemia is considered one of the contraindications for drug use. If blood calcium is not measured before drug use and the patient happens to have hypocalcemia, it is easy to be dangerous.

As long as calcium is supplemented, the bones will not be calcium deficient?

Wrong! To prevent osteoporosis, calcium supplementation alone is not enough. If calcium is the "foundation" of bones, then vitamin D is the carrier that transports the "foundation" to bones. If the body does not have enough vitamin D, even if more calcium is supplemented, the body cannot absorb it effectively. On the other hand, if vitamin D is deficient, it will also cause "secondary hyperparathyroidism", enhance bone absorption, and thus cause and aggravate osteoporosis. Therefore, osteoporosis patients should not forget to supplement vitamin D while supplementing calcium.

Author: Department of Orthopedics, Tianjin Third Central Hospital

Guo ShuzhangChief Physician