SERUM LEVELS OF CROSS-LINKED N-TELOPEPTIDES AND AMINOTERMINAL PROPEPTIDES OF TYPE-I COLLAGEN INDICATE LOW BONE-MINERAL DENSITY IN ELDERLY WOMEN

Levels of aminoterminal propeptide (PINP) and the crosslinked carboxyt erminal (ICTP) and aminoterminal (NTx) telopeptides of type I collagen were determined in the sera of 202 healthy women, 60-90 years of age, and correlated with densitometric measurements of their lumbar spine, femoral neck, and total body regions. Total skeleton bone mineral den sity (BMD) was associated most strongly with serum NTx levels (r = -0. 51, p < 0.0001), Serum NTx and PINP levels correlated with BMD at all regions measured and were significantly increased in osteopenic women (16.0 vs. 13.3 nmol bone collagen equivalents/L for NTx, p = 0.0006 an d 46.5 vs, 40.9 mu g/L for PINP, p = 0.02), Elevations of NTx and PINP over a 3 year interval correlated with decreases in BMD measured at t he femoral neck and to increases in serum concentration of alkaline ph osphatase activity and ICTP, Serum levels of ICTP, NTx, PINP, ICTP, es trone, and alkaline phosphatase activity were correlated and serum NTx values were related to circulating thyroxine and intact parathyroid h ormone levels. NTx and PINP levels were significantly decreased in the sera of women receiving estrogen replacement therapy (12.0 vs. 14.8 n mol bone collagen equivalents/L for NTx, and 35.5 vs. 45.2 mu g/L for PINP, p < 0.001). Multiple regression analysis indicated that 42% of t he variability observed in total skeletal BMD could be explained by ag e, weight, and serum levels of NTx and estrone, Within this model of c ovariance, the serum NTx level alone accounted for 10.1% of total body BMD variability. (C) 1998 by Elsevier Science Inc. All rights reserve d.