Approximately 1 percent of the calcium in your body is located in your blood and soft tissues. The levels of calcium in your blood are tightly controlled by the parathyroid glands, which are four small glands located on the thyroid gland in the front of your neck. The parathyroid glands produce several different hormones that affect the amount of calcium in your blood.
Physiology
Two important hormones, parathyroid hormone and calcitonin, regulate the levels of calcium in your blood. When the calcium levels in your blood decrease, it signals the parathyroid glands to produce more parathyroid hormone, which stimulates the bones to release calcium into the blood. Parathyroid hormones also stimulate your digestive system to absorb more calcium and your kidneys to get rid of less calcium, which can help increase calcium levels in your blood. Normally, when calcium levels return to normal, the production of parathyroid hormone decreases. When calcium levels get too high, the thyroid gland produces calcitonin, which slows the release of calcium from the bone.
Hyperparathyroidism
Hyperparathyroidism is a medical condition characterized by the overactivity of the parathyroid glands. When the parathyroid glands are overactive, they secrete too many hormones. As a result, calcium levels in the blood rise, even when it is not necessary. Excess calcium in the blood, medically referred to as hypercalcemia, can cause weakness, fatigue, muscle pain, nausea, vomiting, constipation, increased thirst and increased urination.
The National Endocrine and Metabolic Diseases Information Service notes that in the majority of hyperparathyroidism cases, no cause can be identified. Surgery to remove the parathyroid glands is the most common treatment for hyperparathyroidism and the resulting high levels of blood calcium.
Hypoparathyroidism
Hypoparathyroidism occurs when the parathyroid glands do not produce enough hormones. As a result, blood calcium levels decrease. Low levels of blood calcium can cause tingling in the extremities, fatigue, weakness, muscle aches, dry skin, brittle nails, headaches, depression and memory problems. Hypoparathyroidism can occur as a result of autoimmune diseases, cancer radiation treatment and low levels of magnesium in the blood. The condition can also be acquired after surgery that destroys the parathyroid glands. Treatment for hypoparathyroidism consists of oral supplementation of calcium carbonate and vitamin D and regular screening of calcium levels.
Considerations
Although parathyroid gland diseases are the most common cause of abnormal calcium levels in the blood, other conditions can disrupt calcium levels as well. Certain medications, dehydration, excess supplementation and infectious diseases can cause high levels of calcium in the blood. Low levels of calcium can occur as a result of autoimmune disorders, inflammation of the pancreas and certain cancers.
