Cross-linked N-eopeptide of type I collagen (NTx) is a specific indicator of bone resorption.
NTx Molecule

The NTx molecule is specific to bone due to the unique amino acid sequence and orientation of the cross-linked alpha-2 (I) N eopeptide
It is generated from bone by osteoclasts as a degradation product of type I collagen, and it can easily be measured in urine or serum using the Osteomark NTx products.