While most doctors tend to monitor bone density with the dual-energy x-ray absorptiomentry (DEXA) test, there is another, less expensive test helpful in determining if you are currently losing bone. This test, called the cross-linked N-teleopeptide (or NTx for short), is a simple urine or blood test known as a “marker of bone resorption.” When you lose bone, small fragments of bone protein show up in the urine and blood, and measuring these bone protein fragments gives an indication of rate of bone breakdown. In most cases a high rate of bone breakdown, also known as bone resorption, indicates that there is an ongoing loss of bone mass.
The bone resorption markers most commonly used are the urine NTx osteomark marker and the urine deoxypyridinium cross-links (Dpd). Your physician can order either of these tests. Generally, a score that’s near or even a bit below the premenopausal mean for women, and one near or even a bit below the young adult mean for men, is ideal. In both tests, the higher the number, the greater the likelihood of a more rapid rate of ongoing bone loss. For more details see my articles on bone density testing and bone resorption testing.