Plasma Monomeric Calcitonin as a Marker of Disease Activity in Multiple Myeloma Patients with Osteolysis

Abstract

Circulating monomeric human calcitonin (hCT-M), parathyroid hormone, osteocalcin, alkaline phosphatase, urinary hydroxyproline, corrected serum calcium and inorganic phosphate were measured in 49 multiple myeloma patients and 49 matched controls. In patients with Durie-Salmon stage III disease hCT-M levels (16.9 ± 5.8 ng/l, mean + SD) were significantly higher than controls and stage I patients (P < 0.01), and correlated directly with corrected serum calcium (r = 0.74; P < 0.001). In the same subgroup 14 of 15 patients had plasma hCT-M concentrations higher than the mean + 2SD of the controls. The calcium infusion test induced an increase of hCT-M in normocalcemic patients which was significantly greater in patients with advanced disease than in either controls or stage I patients. These findings suggest that hCT-M may be a biochemical index of bone resorption and disease activity in myeloma patients with osteolysis. In fact, its plasma concentrations were elevated in a large proportion (93%) of patients with severe bone involvement, and correlated directly with serum calcium. Moreover, our findings suggest the presence of a calcitonin-dependent calcium homeostatic mechanism, that protects against hypercalcemia due to tumor osteolysis.