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This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
Key points
- Confirm true hypercalcemia with albumin-corrected or ionised calcium
- Assess severity and symptoms first: confusion, dehydration, AKI, arrhythmia, and very high calcium require urgent treatment
- PTH is the branching test: high/inappropriately normal PTH suggests primary hyperparathyroidism; suppressed PTH suggests malignancy, vitamin D, granulomatous disease, or drugs
- Primary hyperparathyroidism and malignancy are the two most important adult causes
- Initial severe hypercalcemia treatment is IV isotonic fluids; add antiresorptive therapy and calcitonin according to cause and severity
Approach to the Presentation
Hypercalcemia may be found incidentally or present with fatigue, constipation, abdominal pain, polyuria, polydipsia, nephrolithiasis, bone pain, depression, confusion, shortened QT, or acute kidney injury. The MCCQE1 approach is to confirm the calcium abnormality, determine whether it is symptomatic/severe, and then branch by PTH. PTH-dependent hypercalcemia is most often primary hyperparathyroidism. PTH-independent hypercalcemia raises malignancy, vitamin D intoxication, granulomatous disease, thyrotoxicosis, adrenal insufficiency, immobilisation, and medication causes. Acute management and long-term cause-specific management are separate decisions.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Hypercalcemic Crisis | must-not-miss | Severe calcium elevation with confusion, dehydration, vomiting, AKI, arrhythmia, coma; often malignancy or severe primary hyperparathyroidism | Corrected/ionised calcium markedly elevated plus ECG/renal assessment |
| Malignancy-associated Hypercalcemia | must-not-miss | Weight loss, night sweats, bone pain, smoking history, known cancer; squamous cancers, breast, renal, myeloma, lymphoma | Suppressed PTH; PTHrP, SPEP/UPEP, imaging according to symptoms |
| Multiple Myeloma | must-not-miss | Older adult with bone pain, anaemia, renal impairment, recurrent infections, high calcium | SPEP/UPEP, serum free light chains, skeletal imaging |
| Primary Hyperparathyroidism | common | Often asymptomatic; kidney stones, osteoporosis, constipation, depression, abdominal pain, high-normal or elevated PTH | High calcium with inappropriately high/normal PTH |
| Medication-induced Hypercalcemia | common | Thiazides, lithium, calcium carbonate, vitamin A, vitamin D, supplements; milk-alkali syndrome | Medication history, PTH pattern, renal function, vitamin levels |
| Vitamin D Toxicity | less common | Excess supplementation, granulomatous disease, lymphoma; nausea, weakness, polyuria | Suppressed PTH; high 25-OH vitamin D in overdose or high 1,25-OH2 vitamin D in granulomatous disease/lymphoma |
| Granulomatous Disease | less common | Sarcoidosis, TB, fungal infection; cough, dyspnea, systemic symptoms | Suppressed PTH; high 1,25-OH2 vitamin D; chest imaging and disease-specific tests |
| Thyrotoxicosis or Adrenal Insufficiency | less common | Hyperthyroid symptoms or adrenal symptoms with mild-moderate hypercalcemia | TSH/free T4 or cortisol testing based on context |
| Familial Hypocalciuric Hypercalcemia | rare | Lifelong mild hypercalcemia, family history, asymptomatic, normal/mild high PTH | Low urine calcium/creatinine clearance ratio |
Red Flags & Key History
Symptoms
Confusion, coma, severe weakness, dehydration, vomiting, or arrhythmia symptoms
Oliguria, acute kidney injury, or severe polyuria/polydipsia
Bone pain, weight loss, night sweats, haemoptysis, breast mass, or known malignancy
Recurrent kidney stones or fragility fracture
Very high calcium or rapidly rising calcium
Constipation, abdominal pain, depression, cognitive slowing, fatigue
Medication/supplement use: thiazide, lithium, calcium carbonate, vitamin D, vitamin A
Signs
Dehydration, reduced level of consciousness, or focal neurological compromise
Short QT or arrhythmia on ECG
Bone tenderness, pathological fracture, or spinal cord compression signs
Neck scar or parathyroid/thyroid surgical history
Lymphadenopathy, breast mass, lung findings, or hepatosplenomegaly
Approach to Investigation
First-line
Repeat calcium with albumin or ionised calciumConfirms true hypercalcemia and grades severity
Creatinine/eGFR, electrolytes, phosphate, magnesiumAssess renal effect and associated metabolic pattern
PTHCritical branching test: PTH-dependent versus PTH-independent hypercalcemia
ECGShort QT or arrhythmia in moderate-severe hypercalcemia
Second-line
PTHrP, 25-OH vitamin D, 1,25-OH2 vitamin DUse when PTH is suppressed to evaluate malignancy, vitamin D excess, granulomatous disease, or lymphoma
SPEP/UPEP and serum free light chainsIf anaemia, renal dysfunction, bone pain, or older patient raises myeloma concern
24-hour urine calcium or calcium/creatinine clearance ratioDistinguish primary hyperparathyroidism from familial hypocalciuric hypercalcemia
Specialist
Neck ultrasound/sestamibi or 4D CTLocalisation only after biochemical diagnosis of primary hyperparathyroidism and surgical plan
Oncology imaging/workupIf malignancy-associated hypercalcemia suspected
Endocrinology/nephrology referralSevere, recurrent, unclear, renal impairment, or surgical parathyroid disease
Management Principles
Canadian endocrinology practice informed by Choosing Wisely Canada and endocrine diagnostic standards1
Acute severe hypercalcemia
- Stop calcium/vitamin D, thiazides, lithium if appropriate; treat dehydration
- Give IV isotonic fluids unless contraindicated; monitor urine output and electrolytes
- Add calcitonin for rapid short-term lowering and IV bisphosphonate or denosumab depending cause/renal function and specialist advice
2
PTH-dependent hypercalcemia
- Primary hyperparathyroidism: assess kidney stones, eGFR, bone density, age, calcium level, and surgical criteria
- Refer for parathyroid surgery when criteria met; avoid localisation imaging until surgery is being considered
- FHH: avoid unnecessary parathyroidectomy
3
PTH-independent hypercalcemia
- Investigate malignancy promptly when PTH is suppressed and clinical context suggests cancer
- Treat vitamin D toxicity, granulomatous disease, thyrotoxicosis, adrenal insufficiency, or medication causes specifically
Complications & Pitfalls
- Not correcting for albumin: Apparent calcium abnormalities may reflect albumin rather than ionised calcium
- Skipping PTH: PTH is the central branching test
- Localisation before diagnosis: Parathyroid imaging is not a diagnostic test for hyperparathyroidism
- Missing myeloma: Hypercalcemia + renal dysfunction + anaemia + bone pain should trigger myeloma workup
- Under-treating severe hypercalcemia: Confusion, AKI, and arrhythmia require urgent therapy, not outpatient follow-up
MCCQE1 Exam Tips
- 1Confirm calcium, assess severity, then order PTH
- 2High calcium with non-suppressed PTH = primary hyperparathyroidism until proven otherwise
- 3Suppressed PTH = malignancy/vitamin D/granulomatous/drug causes
- 4Parathyroid scan localises before surgery; it does not diagnose primary hyperparathyroidism
- 5Severe symptomatic hypercalcemia: IV fluids are the first immediate treatment
- 6Myeloma stem: bone pain + anaemia + renal failure + calcium
- 7FHH has low urinary calcium and should not undergo parathyroidectomy
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