Calcium: What is it used for?

DECRYPTING – A dose of this essential mineral for the skeleton is often included in a general blood test. This can highlight a number of issues.

What is it used for?

99% of dietary calcium enters the bones (and teeth) in the form of calcium phosphate. The rest circulates in the blood and is involved in nerve transmission, muscle contractions, clotting, the transfer of information from one cell to another, and various enzymatic reactions that generate energy.

The concentration of calcium in the blood is mainly regulated by parathyroid hormone and vitamin D. If the body lacks calcium (hypocalcemia), the bones release it into the blood to restore the balance. If the amount of calcium in the blood is too high (hypercalcemia), the excess is stored in the bones or excreted in the urine.

When is his dose set?

A calcium test is usually part of a blood test. It can be prescribed for a disorder due to excess or deficiency of calcium. “Hyperparathyroidism (autoimmune abnormality), Kahler’s disease (bone cancer), vitamin D excess, sarcoidosis (inflammatory disease) or Paget’s disease are accompanied by hypercalcemia in children,” explains Dr. François Blanchecotte, National President of the Union of Biologists (SDB). ). Calcium doses are also included in cancer surveillance or osteoporosis evaluation.

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How is it dosed?

Measurement of calcemia is done on an empty stomach, usually with a simple blood test in the bend of the elbow. Most often, the doctor prescribes a dose of the total calcium circulating in the blood. In some cases, to more accurately reflect serum calcium levels, he will ask for “corrected calcium” (which is also taken into account in the albumin test) or, less commonly, “ionized calcium” (the active form of calcium). If the doctor suspects osteoporosis, he or she may ask for a 24-hour urine calcium dose in addition to the “total calcium” level.

How to interpret the results?

Normal value

Total serum calcium is between 2.18 and 2.60 millimoles per liter (mmol/L). This balance is necessary for bones to regenerate daily. A healthy person’s diet, which contains enough dairy products (2 per day), usually provides sufficient calcium. Be careful, the use of certain medicines, such as antacids containing calcium salts, lithium or vitamin D, can interfere with the test results.

Low value

When the calcium level is less than 2.18 mmol/l, it is called hypocalcemia. This can lead to osteoporosis. It is most commonly associated with vitamin D deficiency, kidney tumor, lack of absorption from the gut, or parathyroid hormone deficiency (hypoparathyroidism) caused by an autoimmune disease, removal of the parathyroid glands during thyroidectomy (removal of the thyroid gland). thyroid).

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High value

When the calcium level is higher than 2.60 mmol/l, it is called hypercalcemia. It can be a result of hyperparathyroidism (abnormally high production of parathyroid hormones), blood disease, bone metastases and can lead to urinary stones.

To know

The amount of calcium in the body is determined by diet, calcium absorption in the intestine and the activity of the parathyroid glands.

Calcium values ​​are very stable. When a dose abnormality occurs, it is often interpreted in terms of parathyroid hormone (PTH) and albumin (corrected calcium) dose as well.

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