Hypercalcemia is defined as a serum calcium concentration greater than 2.75 mmol/L.
Etiology
The main causes include:
- Hyperparathyroidism: Often associated with parathyroid adenoma or hyperplasia.
- Malignancies: Conditions such as leukemia, multiple myeloma, or bone metastasis from malignant tumors.
- Vitamin D Toxicity: Long-term excessive intake of vitamin D can lead to vitamin D toxicity, resulting in hypercalcemia and hyperphosphatemia.
Clinical Manifestations
Mild hypercalcemia typically presents with no specific symptoms. As serum calcium levels rise further, especially in patients with concurrent hyperparathyroidism, symptoms may include fatigue, poor concentration, insomnia, depression, delayed tendon reflexes, and reduced muscle strength. Severe cases can result in confusion or even coma.
Nausea, vomiting, and constipation are common among patients with hypercalcemia, while a small number may develop peptic ulcers or pancreatitis. Skeletal involvement includes bone pain, deformities, or pathological fractures. Hypercalcemia may also lead to urinary calculi. Increased myocardial excitability caused by hypercalcemia can result in arrhythmias and heightened sensitivity to digitalis toxicity. Electrocardiograms (ECG) typically show a shortened QT interval, and hypertension is frequently observed in many patients.
Diagnosis
Hypercalcemia can be confirmed when serum calcium levels exceed 2.75 mmol/L, provided serum protein levels are normal. Diagnosis is often based on the patient's medical history, physical examination, and laboratory findings.
Treatment
Management includes addressing the underlying cause and reducing serum calcium levels. Hyperparathyroidism can be cured by surgically removing the adenoma or hyperplastic parathyroid tissue.
Common approaches to lowering serum calcium include:
Promoting Renal Calcium Excretion
Since hypercalcemia is often accompanied by hypovolemia, restoring blood volume can enhance urinary calcium excretion. Loop diuretics can also inhibit calcium reabsorption, thereby increasing urinary calcium elimination.
Inhibiting Bone Resorption
Calcitonin can suppress bone resorption and promote urinary calcium excretion. Zoledronic acid is currently the standard treatment for bone metastases in malignant tumors.
Reducing Intestinal Calcium Absorption
Glucocorticoids can inhibit vitamin D activity, thereby reducing calcium absorption in the gastrointestinal tract and enhancing renal calcium excretion. Oral phosphate preparations may also decrease intestinal calcium absorption.
Dialysis
Dialysis can effectively lower serum calcium levels and is particularly suitable for patients with renal insufficiency or heart failure.