Laboratory and Clinical Findings in Some Disorders Causing Hypercalcemia

Primary hyperparathyroidism

Serum Ca elevated, but < 12 mg/dL (< 3 mmol/L)

Ionized serum Ca > 5.2 mg/dL (> 1.7 mmol/L)

Low serum PO4 (particularly with high renal PO4 excretion)

High alkaline phosphatase (often)

Inappropriately high PTH

Normal or high urinary Ca excretion

Secondary hyperparathyroidism

Serum Ca low, normal, or high, but < 12 mg/dL (< 3mmol/L)

Ionized serum Ca > 5.2 mg/dL (> 1.3 mmol/L)

High serum PO4 (particularly with high renal PO4 excretion)

High alkaline phosphatase (often)

Inappropriately high PTH

Normal or high urinary Ca excretion

Chronic kidney disease (typically)

Humoral hypercalcemia of malignancy

Serum Ca > 12 mg/dL (> 3 mmol/L)

Low PTH

Normal or low PO4

Elevated PTH-related peptide

Possibly metabolic alkalosis, hypochloremia, and hypoalbuminemia

Familial hypocalciuric hypercalcemia

Ratio of Ca clearance to creatinine clearance of < 1%

Hypermagnesemia (often)

High or normal PTH

Life-long and asymptomatic hypercalcemia

Hypercalcemia without hypercalciuria in patients and family members

Milk-alkali syndrome

No hypercalciuria

Metabolic alkalosis

Azotemia (occasionally)

Low PTH (usually)

Normalization of serum Ca when Ca and alkali ingestion stops

High intake of Ca antacids (typically)