What are the most common causes of hypercalcemia?

Primary hyperparathyroidism (usually parathyroid adenoma) causes 90% of outpatient hypercalcemia. Malignancy causes most inpatient hypercalcemia through PTHrP secretion, osteolytic metastases, or 1,25-OH vitamin D production.

What is FHH and how does it mimic hyperparathyroidism?

Familial hypocalciuric hypercalcemia (FHH) is a benign autosomal dominant condition with calcium-sensing receptor mutations causing mild hypercalcemia with inappropriately normal/elevated PTH. Distinguished by urinary calcium:creatinine ratio below 0.01.

When is parathyroidectomy indicated for primary hyperparathyroidism?

Surgery is indicated for: symptomatic disease, serum calcium above 1 mg/dL above normal, age below 50, creatinine clearance below 60 mL/min, T-score at or below -2.5 at any site, or 24h urine calcium above 400 mg.

PTH Interpretation in Context of Calcium

Interpret PTH in context of serum calcium: high Ca + high PTH = primary hyperparathyroidism; high Ca + low PTH = non-PTH-mediated hypercalcemia; low Ca + high PTH = secondary hyperparathyroidism; low Ca + low PTH = hypoparathyroidism.

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Frequently Asked Questions

What are the most common causes of hypercalcemia?

What is FHH and how does it mimic hyperparathyroidism?

When is parathyroidectomy indicated for primary hyperparathyroidism?