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
• 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).