The level of calcium in the blood and tissues is carefully controlled by a number of mechanisms in the body. Abnormally low levels of calcium can occur in a variety of acute and chronic illnesses. Calcium may exist bound to proteins in the blood and as ions in the blood. When the protein levels in the blood become reduced, it will decrease the total amount of calcium present, but may not change the amount of calcium present as ions. Parathyroid hormone is secreted by the four parathyroid glands that are intimately related to the thyroid gland. Parathyroid hormone is responsible for the minute to minute regulation of blood calcium levels within narrow limits. Failure of this mechanism can occur in several instances. Parathyroid hormone may be absent, it may be ineffective or the parathyroid hormone may be overwhelmed by a loss of calcium at a faster rate than it can be replaced.
Causes of Hypocalcemia
Parathyroid hormone may be absent on a congenital basis or in response to surgery of the parathyroid or thyroid glands. Decreased levels of magnesium may produce this condition. Parathyroid hormone may be ineffective in Chronic renal failure, and low levels of vitamin D. The parathyroid hormone may be overwhelmed in situations where tumors are present, there is acute renal failure or there is destruction of large quantities of muscle. These conditions all interfere with the regulation of the calcium levels within the blood. Critically ill patients with sepsis (blood poisoning) and extensive transfusions may develop hypocalcemia. When the pH of the blood become alkaline, the amount of calcium present may be decreased.
Signs and Symptoms of Hypocalcemia
Chronic hypocalcemia frequently produces symptoms. These include muscle spasms, spasms in the hands, facial grimacing and sometimes, spasms of the airway. The pressure within the brain may become elevated with hypocalcemia leading to headaches, nausea and vomiting. It can lead to damage of the optic nerves and confusion. Irritability, depression and psychosis may develop. Irregular heart beats may develop. Acute hypocalcemia may be seen in critically ill patients. Frequently, the reduced protein in the blood is the cause of decreased calcium levels. It occurs from malnutrition or no nutrition during the acute illness. Symptoms may be similar to those seen with chronic hypocalcemia.
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Medical Content Last Updated on 07/12/2008
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