📊 Definitions
• Hypercalcemia: total Ca >10.5 mg/dL (2.6 mmol/L) or ionized Ca >5.3 mg/dL (1.32 mmol/L)
• Symptoms: vomiting, constipation, polyuria (nephrogenic DI), dehydration, confusion, lethargy, coma; EKG shortens QT interval
• "Bones, stones, groans, psychiatric overtones"
🩺 Causes by PTH Level
• High PTH: primary hyperparathyroidism (adenoma, MEN 1/2, hyperparathyroidism-jaw tumor syndrome), tertiary hyperparathyroidism (renal failure)
• Low PTH: malignancy (PTHrP-mediated), vitamin D toxicity, granulomatous disease (sarcoidosis, TB), Williams syndrome, immobilization, thiazide diuretics, milk-alkali syndrome, Jansen metaphyseal chondrodysplasia (PTHR1 mutation)
⚠️ Williams Syndrome
• 7q11.23 deletion (elastin gene), elfin facies, supravalvular aortic stenosis, hypercalcemia (10-15%), developmental delay, friendly personality
• Hypercalcemia often resolves spontaneously; avoid vitamin D, calcium supplements
📋 Treatment
• Mild/moderate: IV fluids (normal saline) to promote calciuresis, loop diuretics (furosemide) after volume repletion
• Severe: calcitonin (4-8 IU/kg SC q12h), bisphosphonates (pamidronate), dialysis
• Chronic: cinacalcet (for hyperparathyroidism), glucocorticoids (for granulomatous disease, vitamin D toxicity)
📌 Decision strategy: Check PTH, vitamin D (25-OH, 1,25-OH), urine calcium/creatinine ratio. High PTH → primary hyperparathyroidism. Low PTH → evaluate for malignancy, granulomatous disease, Williams, vitamin D toxicity.