Although imaging is the first line of diagnosis there is scientific and medical interest in blood or urine tests to aid in uncovering osteoporosis, osteopenia, and other metabolic diseases of the bone. "Bone turnover markers" are chemicals in the bloodstream that may be useful in determining the rate of bone demineralization. BTMs can help tell whether bone disease is happening or immanent and whether treatment – antiresorptive or anabolic - is doing any good.
BTMs are useful in development and proof of efficacy of new drugs. They have other research uses but have not found wide use in clinical diagnostics. Which is too bad because they may have some advantages to the bone mineral density tests currently used.
Bone mineral density (BMD) has its own problems with repeatability, and even with a foolproof method that is lock-tight reliable, BMD can identify a density at a snapshot in time, but to see if things are getting better or worse you have to wait 6 months or a year. BTMs can theoretically (if the test is precise) get at whether the conditions are favorable for bone desorption or deposit of minerals in the bony tissue.
Biomarkers could potentially be useful for choosing treatments. Given the number of different drugs available to manage bone loss, such markers would come in handy.
Biomarkers could also be useful for predicting who is at risk for fracture or for low bone density in the future. They might also prove useful for determining possible causes of secondary osteoporosis.
Deoxypyridinoline is one such physiological marker that shows up in the urine and has been talked about as a useful BTM.
Possible markers that scientists have looked at include soluble receptor activator of nuclear factor-?B ligand-(sRANKL), osteoprotegerin (OPG), and bone alkaline phophatase (BAP),
The sex hormone estradiol. which is tied up with menopause, has also bee mentioned as has the bone protein osteocalcin which is found in the blood in greater concentration when bones are remodeling.
Trace minerals in the blood and bone (zinc, magnesium) have been proposed, and blood, calcium levels are already part of laboratory blood tests when bone disease is known or suspected.
Improvements in automation and standardization of analyses may make clinical use of bone markers viable. Some British scientists claim "BTM levels respond rapidly to both anabolic and antiresorptive treatments" although their paper did not specify which biomarkers they are referring to.
Other Bone Diseases: