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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- First step in confirmed hypercalcemia: measure PTH
- High or inappropriately normal PTH = primary hyperparathyroidism or familial hypocalciuric hypercalcemia
- Suppressed PTH = malignancy, vitamin D excess, granulomatous disease, thyrotoxicosis, medications, or other non-PTH causes
- Severe symptomatic hypercalcemia: isotonic IV fluids first, then calcitonin for rapid short-term effect and IV bisphosphonate/denosumab for sustained effect
- Primary hyperparathyroidism surgery indications include symptoms, kidney stones, osteoporosis/fracture, significant hypercalcemia, reduced kidney function, or young age
Overview
Hypercalcemia is a common electrolyte disorder with causes broadly divided by whether PTH is elevated or suppressed. Primary hyperparathyroidism is the most common outpatient cause and usually results from a single parathyroid adenoma. Malignancy is the most common cause in hospitalized patients and may be mediated by PTH-related peptide, osteolytic metastases, or calcitriol production. Symptoms depend on calcium level and rate of rise, ranging from incidental mild hypercalcemia to life-threatening dehydration, arrhythmia, and coma.
Epidemiology
Primary hyperparathyroidism is more common in women and older adults and is often found incidentally on routine chemistry testing. Malignancy-related hypercalcemia is typically more abrupt and severe, occurring in squamous cell cancers, renal cell carcinoma, breast cancer, multiple myeloma, and lymphoma. Familial hypocalciuric hypercalcemia is benign and important because parathyroidectomy does not correct it.
Clinical Features
Symptoms
Asymptomatic mild hypercalcemia on routine labs
Polyuria, polydipsia, dehydration from nephrogenic diabetes insipidus
Constipation, anorexia, nausea, abdominal pain, pancreatitis
Fatigue, depression, confusion, somnolence, coma in severe hypercalcemia
Bone pain, fragility fractures, kidney stones
Signs
Dehydration, hypertension or shortened QT interval
Nephrolithiasis or flank pain
Proximal muscle weakness
Altered mental status in severe or rapid hypercalcemia
Skeletal tenderness or signs of malignancy when cancer-related
Investigations
First-line
Repeat calcium with albumin or ionized calciumConfirm true hypercalcemia; correct total calcium for low albumin or measure ionized calcium directly
Intact PTHMost important branching test: elevated/inappropriately normal vs suppressed
BMP, phosphorus, magnesium, creatinineAssess renal function, dehydration, and associated electrolyte patterns
Second-line
25-OH vitamin D and 1,25-OH vitamin DEvaluate vitamin D intoxication, deficiency in primary hyperparathyroidism, or granulomatous/lymphoma calcitriol excess
PTHrPIf malignancy-associated humoral hypercalcemia suspected and PTH suppressed
24-hour urine calcium or calcium/creatinine clearance ratioDistinguish primary hyperparathyroidism from familial hypocalciuric hypercalcemia
Specialist
DXA and renal imagingAssess osteoporosis and occult nephrolithiasis in primary hyperparathyroidism
Parathyroid localization imagingSestamibi, ultrasound, or 4D CT only after surgical decision; not for diagnosis
1
Acute severe hypercalcemia
- Isotonic IV fluids first to restore volume and calciuresis
- Calcitonin for rapid temporary reduction while slower agents take effect
- IV zoledronic acid or pamidronate for malignancy-related hypercalcemia; denosumab if renal dysfunction or bisphosphonate-refractory disease
- Loop diuretics only after volume repletion and mainly if fluid overload develops
- Dialysis for life-threatening hypercalcemia with renal failure or inability to tolerate fluids
2
Primary hyperparathyroidism
- Parathyroidectomy for symptomatic disease, kidney stones, osteoporosis/fracture, reduced kidney function, marked hypercalcemia, or younger patients
- Observation may be reasonable for mild asymptomatic disease not meeting criteria
- Hydration, avoid thiazides/lithium if possible, maintain vitamin D repletion, monitor calcium, renal function, and bone density
3
Non-PTH hypercalcemia
- Treat malignancy, stop vitamin D/calcium excess, treat granulomatous disease with glucocorticoids when indicated
- Thyrotoxicosis-related hypercalcemia improves with hyperthyroidism treatment
4
Familial hypocalciuric hypercalcemia
- Low urine calcium and family history; generally benign
- Avoid parathyroidectomy because it does not correct calcium levels
Complications
- Nephrolithiasis and nephrocalcinosis: Calcium stones and chronic renal injury
- Osteoporosis and fractures: Cortical bone loss is classic in primary hyperparathyroidism
- Pancreatitis and peptic ulcer disease: Less common but classically associated
- Arrhythmia: Shortened QT and severe electrolyte disturbance
- Hypercalcemic crisis: Dehydration, AKI, altered mental status, coma
USMLE Step 2 CK Exam Tips
- 1Confirmed hypercalcemia next best step: PTH
- 2High calcium + high PTH = primary hyperparathyroidism until proven otherwise
- 3High calcium + low PTH = malignancy or non-PTH cause
- 4Outpatient hypercalcemia most common cause = primary hyperparathyroidism; inpatient severe hypercalcemia = malignancy
- 5Familial hypocalciuric hypercalcemia has low urine calcium and does not need surgery
- 6Treat severe hypercalcemia with IV normal saline first
- 7Parathyroid imaging localizes before surgery; it does not diagnose primary hyperparathyroidism
- 8Primary hyperparathyroidism classically causes kidney stones and cortical bone loss
practicetest your knowledge on hypercalcemia & primary hyperparathyroidismApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — endocrine and beyond.
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