Calcium is the major component of bone that provides strength. Calcium is absorbed in the small intestines; its absorption is facilitated by vitamin D. Calcium is maintained in the blood by the parathyroid gland, thyroid gland and vitamin D. The heart depends on calcium to function properly; low blood calcium weakens the heart muscle and, when severe, can cause the heart to fail.
Calcium Regulation
Calcium is absorbed from the intestines and is regulated by the parathyroid and thyroid glands. These glands produce parathyroid hormone and calcitonin, respectively. Low blood calcium stimulates the parathyroid gland to produce parathyroid hormone, which acts on bone, causing it to break down and thereby release calcium into the bloodstream. The thyroid gland produces calcitonin in response to elevated calcium in blood; calcitonin causes the removal of calcium from the blood.
Heart Failure
The heart pumps oxygen-rich blood from the lungs to the rest of the body; it also pumps oxygen-poor blood from the body to the lungs. The heart muscle needs calcium to contract properly; very low blood calcium weakens the heart and has been associated with congestive heart failure. When the heart fails, blood flow is affected, and oxygen-rich blood backs up to the lungs. Heart failure must be addressed immediately because it affects the oxygenation of blood.
Complications
Low blood calcium can cause an irregular pulse, but irreversible heart failure, which is rare, can occur when calcium is very low. The parathyroid gland is stimulated to produced parathyroid hormone when blood calcium is low; continued stimulation of the parathyroid gland leads to an excess of parathyroid hormone, which causes excessive bone breakdown. Excess parathyroid hormone weakens bone and makes it more likely to fracture.
Associated Symptoms
Weakening of the heart muscle causes shortness of breath while lying down. A weak heart can lead to leg and belly swelling. Low blood calcium can lead to a condition of uncontrollable muscle contractions called tetany. Tetany may cause odd sensations over the tongue and lips and abnormal twitching of the facial muscles. Excess parathyroid hormone release makes an already weak bone worse. Individuals with excess parathyroid hormone in the blood often complain of bone and joint pain. Generalized weakness, abdominal pain, nausea and depression can also occur.
Warning
An individual with signs of a heart problem like irregular pulse, chest pain or shortness of breath should always consult a physician; this could be a sign of a serious problem.
