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Hypercalcaemia
After correcting for albumin, the separating step is PTH: a high or inappropriately "normal" PTH = primary hyperparathyroidism (or FHH), and a suppressed PTH = another cause, mainly malignancy; severe hypercalcaemia is treated with fluids, calcitonin and zoledronic acid.
Why it matters in the exam
Hypercalcaemia questions usually present an outpatient with an incidentally high calcium (almost always primary hyperparathyroidism) or an inpatient with a tumour, confusion, constipation and dehydration (hypercalcaemia of malignancy). First the calcium is corrected for albumin: add 0.8 mg/dL for every 1 g/dL fall in albumin below 4. Then PTH: if it is high, the differential is primary hyperparathyroidism versus FHH (very low urine calcium, clearance ratio below 0.01); if PTH is suppressed — PTHrP (squamous tumours), calcitriol (lymphoma, sarcoidosis), bone metastases or myeloma, vitamin D excess, thiazides and milk-alkali syndrome.
Severe (above 14 mg/dL) or symptomatic hypercalcaemia is treated with intravenous isotonic fluids, calcitonin for a rapid fall (its effect wanes after 48 hours), and zoledronic acid 4 mg intravenously, which starts working after 2–4 days; in kidney failure denosumab, and in vitamin D-mediated causes (lymphoma, sarcoidosis) — steroids. Loop diuretics are not routine and are given only after volume repletion. In primary hyperparathyroidism the decision on surgery (surgery chapter) rests on a calcium level over 1 mg/dL beyond normal, osteoporosis, eGFR below 60, kidney stones or age under 50.
Key points
- Correct for albumin: 0.8 mg/dL for each 1 g/dL below 4.
- High PTH = parathyroid (or FHH); suppressed PTH = malignancy or vitamin D.
- Severe (above 14 mg/dL): fluids, calcitonin, zoledronic acid 4 mg.
- Denosumab in kidney failure; steroids in lymphoma and sarcoidosis.
- Surgery: calcium above 1 mg/dL over normal, osteoporosis, eGFR below 60, stones, age under 50.
Summary table
| Step | Finding | Meaning / action | Exam note |
|---|---|---|---|
| Albumin correction | +0.8 mg/dL for each 1 g/dL fall below 4 | Decide whether the hypercalcaemia is real | Or measure ionised calcium |
| High or "normal" PTH | Primary hyperparathyroidism | Check urine calcium for FHH | Common in outpatients |
| Suppressed PTH | PTHrP, calcitriol, metastases, myeloma, vitamin D | Look for malignancy | Common in inpatients |
| Severe hypercalcaemia | Above 14 mg/dL or symptoms | Fluids + calcitonin + zoledronic acid 4 mg | Denosumab in kidney failure |
| Vitamin D-mediated | Lymphoma, sarcoidosis | Steroids | High calcitriol |
| Parathyroid surgery | Calcium above 1 mg/dL over normal, osteoporosis, eGFR below 60, stones, age under 50 | Refer to a surgeon | See the surgery chapter |
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Sources
- Endocrine Society Clinical Practice Guideline: Treatment of Hypercalcemia of Malignancy in Adults, 2022 — Bisphosphonates, denosumab, calcitonin and glucocorticoids
- Evaluation and Management of Primary Hyperparathyroidism: Fifth International Workshop, 2022 — Indications for parathyroidectomy
- Harrison's Principles of Internal Medicine, 21st edition (2022) — Disorders of the Parathyroid Gland and Calcium Homeostasis
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.