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Hypercalcemia
(Elevated Calcium Levels)

Hypercalcemia Overview

One of the minerals that is important in the regulation and processes of many body functions including bone formation, hormone release, muscle contraction, and nerve and brain function is calcium. If levels of calcium in the body are elevated above what is considered normal, this is referred to as hypercalcemia.

Calcium levels in the body are tightly regulated. The regulation of calcium is primarily controlled by vitamin D, calcitonin, and parathyroid hormone (PTH).

Calcitonin is produced in specialized cells in the thyroid gland.
Vitamin D is obtained through a process that begins with sun exposure to the skin. The process then continues in the liver and kidneys. Vitamin D can also be found in foods, such as eggs and dairy products.
Parathyroid hormone is a hormone produced by the parathyroid glands, which are four small glands surrounded by the thyroid and found in the anterior part of the lower neck.

Together, the parathyroid hormone, calcitonin, and vitamin D regulate calcium levels in the bloodstream via the kidneys, and the intestinal tract.

Picture of the thyroid and parathyroid glands

Hypercalcemia Causes

The most common cause of high calcium levels (hypercalcemia) is an overproduction of parathyroid hormone, or hyperparathyroidism. Hyperparathyroidism tends to be more common in women, and occurs in 25 out of every 100,000 individuals. Hyperparathyroidism can be the result of all four parathyroid glands producing an excessive amount of parathyroid hyperplasia (PTH), or the result of just one gland specifically producing an excessive amount of PTH (usually the result of a parathyroid adenoma or benign tumor).

Other medical conditions can be associated with high calcium levels (non-parathyroid hypercalcemia). Some of these conditions are not serious; however, they may vary in severity and chronicity. For example, hypocalciuric hypercalcemia is an inherited condition in which individuals do not excrete normal amounts of calcium, thus calcium levels are usually slightly elevated. Patients with hypocalciuric hypercalcemia have little or no symptoms so it is generally discovered incidentally through routine blood tests. Other causes of hypercalcemia can be life-threatening. Cancers are commonly associated with elevated calcium levels and are referred to as "hypercalcemia of malignancy." Twenty to forty percent of patients with cancer will develop hypercalcemia at some point in their disease.

Other conditions associated with hypercalcemia include:

cancers, particularly multiple myeloma, breast cancer and lung cancer;
excessive levels of vitamin D from vitamins, excessive dietary calcium, or from diseases that may result in excess vitamin D production;
immobilization over a long period of time;
inherited metabolic or kidney conditions;
kidney failure;
overactive thyroid (hyperthyroidism) or excessive thyroid hormone intake; and
use of certain medications such as thiazide diuretics.