Hypercalcemia
Hypercalcemia is a total serum calcium concentration of > 10.5 mg/dL (> 2.62 mmol/L) or ionized (free) calcium concentration of > 5.25 mg/dL (> 1.31 mmol/L).
Tip
- Total protein normal level 6.0 to 8.3 g/dL (60 to 83 g/L)
- Albumin normal level 3.4 to 5.4 g/dL (34 to 54 g/L)
- Phosphorus normal level 2.5 to 4.5 g/dL (25 to 45 g/L)
Causes
PTH-mediated or non-PTH-mediated causes
Mnemonic
For causes of hypercalcemia, remember “Thinking Chimpanzees!”
- Thinking: Thiazides, thyroid
- Calcium supplementation
- Hyperparathyroidism
- Immobilization, inherited (FHH)
- Milk-alkali synd., meds (thiazides, lithium)
- Paraneoplastic PTHrP
- Adrenal insufficiency
- Neoplasm (multiple myeloma, breast, lung)
- Zollinger-Ellison syndrome
- Excessive vitamin D
- Excessive vitamin A
- Sarcoidosis & granulomatous diseases
Clinical features
- Nephrolithiasis, nephrocalcinosis (calcium oxalate > calcium phosphate stones)
- Bone pain, arthralgias, myalgias, fractures
- Because most of the calcium is released from bones
- Constipation
- Increase in extracellular Ca2+ → membrane potential outside is more positive → more amount of depolarization is needed to initiate action potential → decreased excitability of muscle and nerve tissue
- Abdominal pain
- Nausea and vomiting
- Anorexia
- Peptic ulcer disease
- hypercalcemia-induced increase of gastric acid secretion and gastrin levels.
- Neuropsychiatric symptoms such as anxiety, depression, fatigue, and cognitive dysfunction
- Diminished muscle excitability
- Cardiac arrhythmias
- ECG: Shorten QT interval, see ECGs#QT interval
- Muscle weakness, paresis
- Cardiac arrhythmias
- Polyuria and dehydration
- Due to acquired renal ADH resistance. Although ADH is being secreted, the kidneys no longer respond to it adequately (nephrogenic diabetes insipidus).
Treatment
- Consider calcitonin for rapid-onset, short-term control of hypercalcemia.
- Bisphosphonates for slow-onset, long-term control of hypercalcemia