Hypercalcemia is a condition where blood calcium levels are higher than normal. While calcium is vital for strong bones and teeth, it also plays roles in nerve function, muscle contraction, blood clotting, and heart rhythm. When calcium levels become too high, this balance is disrupted, affecting various bodily systems. Elevated calcium in a blood test always warrants further investigation to determine the underlying cause.
Parathyroid Gland Involvement
The parathyroid glands are four small glands located behind the thyroid gland in the neck. These glands produce parathyroid hormone (PTH), a central regulator of blood calcium levels. Normally, when blood calcium levels decrease, the parathyroid glands release PTH to restore balance. Parathyroid hormone works by signaling bones to release calcium into the bloodstream, increasing calcium absorption from food in the intestines, and prompting the kidneys to reabsorb more calcium rather than excrete it.
The most frequent reason for elevated calcium is primary hyperparathyroidism. This occurs when one or more of the parathyroid glands become overactive, often due to a benign tumor called an adenoma, or less commonly, an enlargement of all four glands. This overactivity leads to an excessive production of PTH, even when blood calcium levels are already sufficient. The continuously high levels of PTH then cause a persistent increase in blood calcium. This condition typically develops slowly over time.
Hypercalcemia Related to Cancer
High calcium levels can also arise in individuals with cancer. This phenomenon, termed hypercalcemia of malignancy, occurs through mechanisms linked to tumor activity. One way is through bone metastasis, where cancer cells spread to the bones and stimulate the breakdown of bone tissue. This process releases calcium stored in the bones directly into the bloodstream.
Another mechanism involves certain tumors producing hormone-like substances that mimic the action of parathyroid hormone. Parathyroid hormone-related protein (PTHrP) is a common example, which can bind to PTH receptors in the body, leading to increased calcium reabsorption by the kidneys and enhanced bone resorption. Less commonly, some cancers, particularly certain lymphomas, can produce active vitamin D, further increasing calcium absorption from the intestines. Cancers most often associated with elevated calcium include lung cancer, breast cancer, multiple myeloma, kidney cancer, and lymphomas.
Other Contributing Factors
Beyond parathyroid issues and cancer, other factors can contribute to elevated calcium levels. Consuming excessive amounts of vitamin D through supplements can lead to high calcium, as vitamin D enhances calcium absorption from the gut. Certain medical conditions, such as granulomatous diseases like sarcoidosis or tuberculosis, can also cause the body to produce too much active vitamin D.
Some medications can affect calcium regulation in the body. Thiazide diuretics, often prescribed for high blood pressure, can reduce the excretion of calcium by the kidneys, thereby increasing blood calcium levels. Lithium, a medication used for mood disorders, may also lead to mild hypercalcemia by influencing parathyroid hormone release. Severe dehydration can also result in higher calcium concentrations because the blood becomes more concentrated.
A rare, inherited condition called familial hypocalciuric hypercalcemia (FHH) is another potential cause. In FHH, the body’s calcium-sensing receptors are less sensitive to calcium, leading to slightly elevated blood calcium levels that are typically benign and do not require treatment. An overactive thyroid gland, a condition known as hyperthyroidism, can sometimes lead to mild increases in blood calcium. This occurs because elevated thyroid hormones can stimulate bone turnover, releasing calcium into the bloodstream. Prolonged periods of inactivity, such as extended bed rest after a severe injury, can also cause calcium to leach from bones into the bloodstream.
Recognizing the Signs and Next Steps
Symptoms of high calcium levels vary significantly among individuals. In mild cases, people may experience no noticeable symptoms. However, as calcium levels increase, symptoms can emerge, impacting various bodily systems.
Common signs include fatigue, increased thirst and more frequent urination, constipation, and nausea. Some individuals might also experience bone pain, muscle weakness, or changes in cognitive function such as confusion. The formation of kidney stones is another potential outcome of persistently elevated calcium.
If you have received a blood test result indicating high calcium levels or are experiencing any of these related symptoms, it is important to consult a healthcare professional. Only a medical doctor can accurately diagnose the underlying cause of hypercalcemia and recommend appropriate management or treatment.