Hypercalcemia, commonly known as high blood calcium, is a condition where the concentration of calcium in the bloodstream rises above the normal range. Calcium is one of the body’s most abundant minerals, and its precise regulation is important for many physiological processes. When this balance is disrupted, excess calcium can interfere with the normal function of various organs and systems. While mild cases may not cause noticeable symptoms, significantly elevated levels require medical attention to prevent severe complications.
Understanding Calcium’s Role and Normal Levels
Calcium is a fundamental substance involved in far more than just building strong bones. This mineral is necessary for the transmission of nerve signals and allows the brain to communicate effectively with the rest of the body. Within the muscles, calcium ions are released in response to a nerve impulse, triggering the interaction between muscle fibers that results in contraction.
The heart muscle also relies on calcium to maintain its regular rhythm and pumping action. The body maintains the total serum calcium concentration within a tight reference range, typically between 8.5 and 10.2 milligrams per deciliter (mg/dL) in adults. Hypercalcemia is defined as a total serum calcium level exceeding 10.2 or 10.5 mg/dL. Levels above 14 mg/dL are considered severe and potentially life-threatening.
Primary Causes of Elevated Blood Calcium
The majority of hypercalcemia cases stem from a disruption in the body’s hormonal control of calcium, often involving the parathyroid glands or a malignancy.
Primary Hyperparathyroidism
The most frequent cause in outpatient settings is primary hyperparathyroidism, where one or more of the four small parathyroid glands become overactive. These glands, located behind the thyroid in the neck, produce excessive amounts of parathyroid hormone (PTH). The surplus of PTH acts on the bones to increase the release of stored calcium into the bloodstream and signals the kidneys to reabsorb more calcium. This uncontrolled release and retention leads to persistently elevated blood levels. Primary hyperparathyroidism is often characterized by chronically mild hypercalcemia, which can be diagnosed incidentally during routine blood work.
Hypercalcemia of Malignancy
The second most common cause, particularly in hospitalized patients, is hypercalcemia of malignancy, seen in various types of cancer. This form often results in higher calcium levels and a more rapid onset of symptoms. In many cases, tumor cells secrete parathyroid hormone-related peptide (PTHrP). PTHrP mimics the action of natural PTH, causing increased calcium release from bone and reduced kidney excretion. Other mechanisms include direct destruction of bone tissue by metastatic tumors, such as in multiple myeloma, or the production of active Vitamin D by certain lymphomas. Less common causes involve certain medications like thiazide diuretics, which reduce calcium excretion, or excessive intake of Vitamin D supplements.
Recognizing the Physical Effects
Elevated calcium concentrations interfere with normal cell function across multiple organ systems, leading to a range of physical manifestations.
Renal and Gastrointestinal Effects
The kidneys are particularly affected as they attempt to filter the excess calcium from the blood. This increased workload can impair the kidneys’ ability to concentrate urine, resulting in polyuria (frequent urination) and excessive thirst. High calcium levels can lead to the precipitation of calcium crystals, potentially forming painful kidney stones or causing damage to the renal tubules. The gastrointestinal system reacts with symptoms like nausea, vomiting, loss of appetite, and constipation, related to calcium’s effect on smooth muscle contraction.
Neuromuscular and Skeletal Effects
The nervous system and muscles are highly sensitive to calcium imbalance. Neuromuscular effects include generalized fatigue, muscle weakness, and reduced reflexes. Higher calcium levels can slow electrical activity in the brain, manifesting as confusion, lethargy, memory problems, or depression. The skeletal system suffers because the elevated blood calcium frequently originates from the bones themselves, leading to bone resorption. This constant leaching weakens the bone structure, causing bone pain, an increased risk of fractures, and the development of osteoporosis. Severe hypercalcemia can also affect the heart’s electrical system, causing abnormal heart rhythms.
Diagnosis and Treatment Approaches
The diagnosis of hypercalcemia begins with a routine blood test revealing an elevated serum calcium level. Once confirmed, a doctor orders additional blood work to measure the parathyroid hormone (PTH) level, which is key to determining the underlying cause. A high or inappropriately normal PTH level alongside high calcium suggests primary hyperparathyroidism. Conversely, a suppressed or low PTH level points toward a non-parathyroid cause, such as malignancy or Vitamin D excess. Further investigation may involve measuring PTH-related peptide (PTHrP) or Vitamin D levels to pinpoint the specific etiology.
Treatment strategies are divided between immediate management and long-term care focused on the root cause. Acute, severe hypercalcemia is a medical emergency often treated with aggressive intravenous hydration, which helps the kidneys excrete the excess calcium. Medications such as bisphosphonates are administered intravenously to rapidly inhibit the breakdown of bone, thereby lowering blood calcium levels.
For long-term management of primary hyperparathyroidism, surgical removal of the overactive parathyroid gland, known as parathyroidectomy, is often curative. When hypercalcemia is due to cancer, the primary treatment involves addressing the malignancy itself with chemotherapy, radiation, or other therapies. Specialized drugs like calcitonin or denosumab may also be used to help control the calcium levels.