What is Hypercalcemia?
Hypercalcemia is the medical term for having higher-than-normal levels of calcium in your blood. While a majority of the body's calcium is stored in the bones, a small amount circulates in the blood to help nerve function, muscle contraction, blood clotting, and heart rhythm. The body tightly regulates these levels, primarily using parathyroid hormone (PTH) and calcitonin, along with the help of vitamin D. When this delicate balance is disrupted, blood calcium levels can rise, leading to hypercalcemia.
Primary Causes of High Calcium Levels
The two most common reasons for hypercalcemia, accounting for about 90% of cases, are issues with the parathyroid glands and certain types of cancer.
Overactive Parathyroid Glands (Hyperparathyroidism)
This is the most frequent cause of high blood calcium in the general population, especially in postmenopausal women. The four tiny parathyroid glands, located behind the thyroid gland in the neck, produce parathyroid hormone (PTH) to regulate calcium levels. When one or more of these glands become overactive (hyperparathyroidism), they release too much PTH, which triggers the bones to release excess calcium into the bloodstream. The overactivity is most often caused by a benign growth (adenoma) on one of the glands, or sometimes an enlargement of all four glands (hyperplasia).
Cancer (Malignancy)
Cancer-related hypercalcemia (hypercalcemia of malignancy) is the most common cause in hospitalized patients and can occur through several mechanisms.
- Humoral Hypercalcemia of Malignancy (HHM): This is the most common cancer-related cause, where tumors secrete a protein similar to PTH, called parathyroid hormone-related peptide (PTHrP). This substance mimics the effects of PTH, causing bones to release calcium and the kidneys to retain it. This mechanism is often associated with squamous cell cancers, such as those of the lung and head and neck, as well as breast cancer.
- Bone Metastases: Cancer that has spread to the bones can cause them to break down (osteolysis), directly releasing large amounts of calcium into the bloodstream. This is frequently seen in cases of multiple myeloma, breast cancer, and prostate cancer.
- Production of Vitamin D: Some cancers, particularly lymphomas, can produce excessive amounts of activated vitamin D, which dramatically increases calcium absorption from the gut.
Other Potential Causes
Beyond the primary culprits, several other factors can lead to an increase in blood calcium levels.
Excessive Vitamin and Supplement Intake
Consuming very high doses of certain supplements can disrupt calcium balance.
- Vitamin D: Large, prolonged doses of vitamin D supplements can lead to toxicity, causing increased absorption of calcium from the digestive tract.
- Calcium Supplements: Excessive intake of calcium supplements, often combined with calcium-containing antacids, can cause a condition known as milk-alkali syndrome.
- Vitamin A: Over-supplementation of Vitamin A can lead to bone turnover and release of calcium.
Medications
Certain drugs can interfere with the body's calcium regulation.
- Thiazide diuretics: These medications, used for high blood pressure and edema, can cause the kidneys to excrete less calcium.
- Lithium: This drug, used to treat bipolar disorder, can affect parathyroid gland function.
Other Medical Conditions
A variety of other diseases can cause hypercalcemia.
- Granulomatous diseases: Conditions like sarcoidosis and tuberculosis cause the body to produce extra activated vitamin D.
- Chronic Kidney Disease: Long-standing kidney issues can lead to secondary hyperparathyroidism, and in some cases, tertiary hyperparathyroidism with high calcium.
- Inherited Disorders: Rare genetic conditions, such as familial hypocalciuric hypercalcemia, affect how the body senses calcium.
- Thyrotoxicosis: An overactive thyroid gland can increase bone breakdown and calcium release.
Lifestyle Factors
Prolonged inactivity, such as being bedridden, can weaken bones and cause calcium to leach into the blood. Severe dehydration also concentrates the blood, leading to a temporarily higher calcium reading.
Common Causes of Hypercalcemia: A Comparison
| Feature | Primary Hyperparathyroidism (PHPT) | Hypercalcemia of Malignancy (HCM) |
|---|---|---|
| Cause | Overactive parathyroid glands, typically a benign adenoma or hyperplasia. | Cancer cells causing bone destruction or secreting PTH-related protein (PTHrP). |
| Onset | Often slow and gradual, potentially discovered incidentally during routine tests. | Often rapid, severe, and associated with more advanced-stage cancer. |
| Mechanism | Excessive PTH release signals bones to release calcium and kidneys to reabsorb it. | Tumor-secreted proteins mimic PTH or direct bone breakdown occurs. |
| Key Lab Indicators | Elevated PTH and elevated calcium. | Elevated calcium, typically suppressed PTH, and sometimes elevated PTHrP. |
Symptoms of High Calcium
The symptoms of hypercalcemia can be vague and depend on the severity and duration of the condition. In mild cases, there may be no noticeable symptoms, while severe cases can cause significant issues.
Common Symptoms of Hypercalcemia:
- Kidney-related: Excessive thirst and frequent urination, potentially leading to dehydration. Over time, this can lead to painful kidney stones.
- Digestive Issues: Constipation, nausea, vomiting, stomach pain, and loss of appetite.
- Bone and Muscle Problems: Bone pain, muscle weakness, and, in severe cases, fractures due to weakened bones.
- Neurological Symptoms: Fatigue, lethargy, confusion, memory problems, and depression.
- Cardiac Effects: Abnormal heart rhythms (arrhythmia), which can be serious.
What to do if Your Blood Test Shows High Calcium
An elevated calcium reading is not an immediate cause for panic, but it does warrant further investigation by a healthcare professional. The initial step is often a repeat blood test to confirm the result, as factors like dehydration can cause a temporary spike. Your doctor will then likely perform additional tests to pinpoint the cause.
Following a confirmed diagnosis, treatment will depend on the underlying cause and severity. For example, if hyperparathyroidism is the cause, surgery to remove the affected gland is often curative. If cancer is the cause, treatment will focus on addressing the malignancy itself, sometimes using medications like bisphosphonates to help lower calcium levels. In severe cases, hospital treatment with intravenous fluids may be necessary.
Conclusion: Next Steps Following an Elevated Calcium Result
In summary, an elevated calcium level on a blood test, or hypercalcemia, has a number of potential causes, with primary hyperparathyroidism and cancer being the most common. Other causes include over-supplementation, medications, and certain medical conditions. While mild cases may have no symptoms, severe or prolonged hypercalcemia can lead to serious complications involving the kidneys, bones, and heart. The discovery of high calcium should always be followed up with a doctor to confirm the reading and determine the root cause through further diagnostic tests. Seeking professional medical advice is the most important step towards proper management and treatment. For more information, you can read about hypercalcemia on authoritative sites like the Mayo Clinic.
