In order to clarify the pathogenesis of hypercalcemia in multiple myeloma, we measured
plasma levels of parathyroid hormone related peptide (PTHrP), tumor necrosis factor
α (TNF-α), tumor necrosis factor β (TNF-β), intact PTH and, serum 1,25-dihydroxyvitamin
D in fifteen patients of multiple myeloma. We also measured serum levels of inorganic
phosphorus (iP) and alkalinephosphatase activity (ALP). No significant differences
in iP (3.2 ± 0.4 vs. 4.0 ± 2.2 mg/dl), ALP (150 ± 28 vs. 335 ± 305 IU/l) 1,25(OH)2
D (31.5 ± 17.0 vs. 23.3 ± 11.2 pg/ml) or TNF-α (7.8 ± 2.1 vs. 8.0 ± 2.0 pg/ml) were
observed between normocalcemic and hypercalcemic patients. Plasma iPTH levels in hypercalcemic
patients were significantly lower than those in normocalcemic patients (28.5 ± 9.4
vs. 16.3 ± 5.6 pg/ml, p = 0.01). Plasma levels of TNF-β were less than 15.6 pg/ml
in all subjects. On the other hand, the frequency of patients with abnormally high
plasma levels of PTHrP was significantly greater (2/9 for normocalcemia vs 5/6 for
hypercalcemia, χ2 = 5.20, p = 0.02) in patients with hypercalcemia than in normocalcemic
patients. Furthermore, a significant positive relationship between plasma PTHrP levels
and corrected serum calcium levels (cCa) was observed using Spearman's correlation
analysis by rank in fifteen myeloma cases (rs = 0.66, p = 0.013). These results suggest
that PTHrP might be involved in the elevation of serum calcium levels in hypercalcemic
myeloma patients. However, a few cases exhibit normocalcemia despite elevated plasma
PTHrP levels or hypercalcemia without high plasma PTHrP levels. Therefore, further
studies are necessary to elucidate the pathogenesis of hypercalcemia in multiple myeloma.
Key words
Parathyroid hormone related peptide (PTHrP) - Multiple myeloma (M. M.) - Hypercalcemia
