Urinary cross-linked N-telopeptides of type I collagen and bone metabolic diseases

Objective To evaluate the type I collagen crosslinked N-telopeptide (NTx) l evels in human urine as an indicator of bone resorption rate in different a ges, sex and in bone metabolic diseases. Methods Urinary NTx was determined by immunoassay in 591 Beijing healthy su bjects aged from 0 to 86 years and 379 patients with bone metabolic disease s. Results The levels of urinary NTx were significantly higher in children tha n in adults (P < 0.001) and higher in boys than in girls (P < 0.01) and inc reased 1.4-2.2 times in postmenopausal females than in men and premenopausa l women. Urine NTx had a positive linear correlation with urine HOP/Cr (r=0 .778, P< 0.01) and Ca/Cr ratio (r= 0.320, P< 0.01), and a negative linear c orrelation with age (r= -0.523, P < 0.01) and lumbar spine BMD (r = -0.426, P < 0.01). The levels of urine NTx increased for 3.6 times in pregnancy, 1 .5 times in osteoporosis, 1.9 times in fragility fracture, 3.6 times in chr onic renal failure, 2.1 times in rickets and 7.2 times in multiple myeloma compared to age matched controls. Conclusions NTx in urine is a specific and sensitive indicator of bone reso rption and is able to distingish normal premenopause from late osteoporotic patients. NTx could be used as diagnostic information about metabolic bone diseases, and to monitor antiresorptive therapy.