Low calcium level in the blood or hypocalcemia is a disorder of calcium ions balance in the body in which there is abnormally low concentration of calcium in the blood below its normal physiological value. Hypocalcemia can have several causes that will be mentioned in this article.
Calcium is an alkaline earth metal ion which has an important role in the body. There are two main roles to calcium in the body. These are: maintaining appropriate level of bone density by keeping calcium salts deposition on the bone tissue. In addition calcium is important for the function of muscles by inducing muscles contraction and relaxation.
Also calcium ions can function as cofactors for enzymes such as its function to assist the hormone insulin in doing its job in the body of glucose transport across the cellular membrane. Due to these important roles of calcium in the body nature has designed two hormones to regulate the level of this ion in the blood in addition to one vitamin (vitamin D) which functions to increase the absorption of calcium in the small intestine. Thus helping in promoting the level of calcium in the body.
The two hormones that are important for the regulation of calcium in the body are called parathyroid hormone and calcitonin. Parathyroid hormone is the more important physiologically and clinically among the two hormones. It is usually secreted in physiological amounts to the blood circulation by the parathyroid gland in response to a state of hypocalcemia or deficiency in the amount of calcium in the blood.
It is regulated by a negative feedback in which increased amount of calcium ions in the blood inhibits its secretion by the parathyroid gland. This hormone increases the amount of calcium ions in the blood indirectly by affecting the function of one bone cell type which is called osteoclasts. This hormone stimulates these cells to release calcium from the bone tissue to the blood circulation. Thus increasing its concentration in the blood.
The other hormone which has an effect on calcium level in the blood is called calcitonin. This hormone is secreted by the thyroid gland from its parafollicular cells. It is secreted in response to high level of calcium ions in the blood or hypercalcemia. This hormone stimulates the deposition of calcium salts on the bone tissue. It does this indirectly by stimulating the other cell type of the bone tissue which is called osteoblasts.
These cells signal the deposition of calcium salts on the bone tissue by a stimulus from the hormone calcitonin. Also in addition to these two hormones the vitamin D is another factor in the development of hypocalcemia and hypercalcemia. Vitamin D is usually obtained in the diet in the form of tablets.
Also it is synthesized by cells of the kidney from precursor molecules. Its excess can cause a state of hypercalcemia while its deficiency can cause a state of hypocalcemia as will be seen shortly. There are three main causes to hypocalcemia that will be mentioned here. First a state of decreased secretion of the parathyroid hormone or hypoparathyroidism can cause a state of hypocalcemia or decreased amount of calcium ions in the blood.
This condition of hypoparathyroidism is caused in most cases due to surgery to the nck region which is usually done on the thyroid gland to remove part of a hyperactive gland. As a result of such a surgery a damage to the parathyroid gland can occur for example through the destruction of the blood supply to these four glands.
It can also be caused due to surgery to these parathyroid glands which can be hyperactive, oversecreting the parathyroid hormone. This type of surgery usually can cause hypofunctional parathyroid glands with subsequent development of hypocalcemia. A common complication of such a surgery involves the destruction of the laryngeal nerve which would result in loosing the voice of the affected individual.
Also magnesium deficiency in the body can cause a state of hypocalcemiasince magnesium is an agonist to calcium in the body. Its excess causes excess of calcium and vice versa. Thus one symptom of magnesium deficiency in the blood is development of hypocalcemia also.