ABNORMAL BONE TURNOVER IN MONOCLONAL GAMMOPATHY OF UNDETERMINED SIGNIFICANCE - ANALYSES OF TYPE-I COLLAGEN TELOPEPTIDE, OSTEOCALCIN, BONE-SPECIFIC ALKALINE-PHOSPHATASE AND PROPEPTIDES OF TYPE-I AND TYPE-III PROCOLLAGENS

The main difference between monoclonal gammopathy of undetermined sign ificance (MGUS) and multiple myeloma (MM) is the presence of lytic bon e destructions in the latter. About 20% of MGUS patients develop MM, a nd histomorphometric studies have shown disturbed bone turnover rates in some of these patients. This study was performed in order to evalua te whether serum analyses of the C-terminal telopeptide of type I coll agen (ICTP), as a reflector of bone degradation, and of osteocalcin, b one-specific alkaline phosphatase (bAP) and the C-terminal propeptide of type I procollagen (PICP), as markers of bone formation, might give information on disturbancies of bone metabolism in MGUS. Furthermore, serum N-terminal propeptide of procollagen III (PIIINP) might give in formation on disturbances in collagen III metabolism in the bone marro w In the 35 patients examined, serum ICTP was elevated in 12 patients (34%), serum PIIINP elevated in 6 patients (17%), serum osteocalcin el evated in 11 patients (31%), serum bAP elevated in 6 patients (17%), a nd serum PICP elevated in 4 patients (11%). Serum ICTP correlated sign ificantly with PIIINP (r=0.72, p<0.001), and with serum osteocalcin (r =0.57, p<0.001) and serum bAP (r=0.51, p=0.002). These findings indica te disturbancies of bone turnover and affected collagen metabolism in some MGUS patients. Followup observation may reveal any prognostic val ue of these findings.