Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1103 page)

   HHM occurs in patients with cancer (typically squamous, transitional cell, renal, ovarian), 5–20% who have no bone metastases compared to patients with widespread bone metastases (myeloma, lymphoma, breast cancer).

   HHM occurs in approximately 20–35% of patients with breast cancer, approximately 10–15% of cases with lung cancer, approximately 70% of cases with multiple myeloma, and rare in lymphoma and leukemia.

   Rarely hypercalcemia may occur in association with benign tumors (e.g., pheochromocytoma, dermoid cyst of the ovary) (“humoral hypercalcemia of benignancy”).

   Very high serum calcium (e.g., >14.5 mg/dL) is much more suggestive of HHM than primary HPT; less marked increase with renal tumors. Less than or equal to 5% of hypercalcemia patients have simultaneous HPT and HHM.

   Interpretation

Increased In

   Increased serum PTHrP (>2.6 pmol/L) can make a positive diagnosis in most cases of HHM, but approximately 20% of cancer patients with hypercalcemia have only local osteolytic changes with no increased PTHrP.

   PTHrP is also increased in (>2.6 pmol/L)

   Greater than 80% of hypercalcemic patients with solid tumors with or without bone metastasis.

   Some patients with hypercalcemia and hematologic cancers.

   Approximately 10% of cancers without hypercalcemia; PTHrP becomes normal when hypercalcemia is corrected by treatment of cancer.

   May be increased in nonmalignant pheochromocytoma.

Normal In

   Healthy persons: values <1.0 pmol/L.

   Other causes of hypercalcemia (e.g., sarcoidosis, vitamin D intoxication).