SERUM BETA-2-MICROGLOBULIN IS A MARKER OF HIGH BONE REMODELING IN ELDERLY WOMEN

beta-2 microglobulin (beta 2m), the water soluble extrinsic light chai n of class I MHC, has been recently isolated from the adult bone cultu re medium. Serum beta 2m plays a role as a bone-derived growth factor regulating both osteoblast and osteoclast cell activity. Serum beta 2m has been proposed as a bone remodeling biological marker in high bone turnover conditions. The purpose of our study was to determine the re lationship between beta 2m and vitamin D status in post-menopausal wom en. We have studied 44 healthy women from 20 to 80 years with normal h epatic and renal function, without diabetes mellitus and/or inflammato ry, tumoral or infectious diseases. We measured the serum levels of ca lcium. phosphorus, parathyroid hormone (PTH), vitamin D binding protei n (DBP), 25-OHD, (calcidiol), 1,25(OH)(2)D-3 (calcitriol) and beta 2m. Serum beta 2m levels increased with age (r = 0.54, P < 0.001). Post-m enopausal women had higher serum levels than pre-menopausal women of b eta 2m (1.76 +/- 0.22 mg/l vs. 1.35 +/- 0.2 mg/l, P < 0.01); PTH (61.5 +/- 7.5 ng/ml vs. 39 +/- 6 ng/ml, P < 0.001) and lower serum levels o f 25-OHD, (7.5 +/- 2.3 ng/ml vs. 18.2 +/- 2.5 ng/ml, P<0.001). Moreove r, serum levels of beta 2m were negatively correlated with 25-OHD, (r = - 0.34, P < 0.05) and with ionized calcium (r = - 0.45, P<0.01) and positively with PTH (r = 0.48, P < 0.01). These results support the ro le of beta 2m as a regulator of bone metabolism and its potential use as a marker of high bone turnover in post-menopausal women, specially in elderly women with vitamin D deficiency and secondary hyperparathyr oidism. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.