With the increased use of bone density measurements, osteoporosis can now be more easily diagnosed and treated. This has prompted the scientific community's strong interest in the biochemical markers of bone metabolism. The bones are constantly recycled, absorbed, and reshaped. Osteoclasts absorb bone, and osteoblasts produce bone. Osteoporosis is a common disease of postmenopausal women and is associated with increased bone resorption and reduced bone formation. The result is the creation of thin, weak bones prone to fractures. Osteoporosis is now increasingly recognized in older men. Early diagnosis allows therapeutic intervention and prevention of bone fractures.
Bone density measurement is a valuable tool in determining osteoporosis, but it cannot detect small changes in bone metabolism. Although bone density measurements can be used to monitor the effectiveness of treatment, it may take years to detect measurable changes in bone density. However, biochemical Bone Turnover Markers (BTMs) can identify any changes within a few months of applying a successful treatment. In addition, the cost of measuring BTMs is generally lower than the corresponding cost of measuring bone density.
Because levels of Biochemical Bone Turnover Markers vary with time of day and bone volume, their measurements are not used as routine tests to detect osteoporosis. Their use is constructive in evaluating treatment efficacy by comparing them with the corresponding values before treatment is applied. BTM levels are reduced by anti-absorption drugs (e.g., estrogens, bisphosphonates, calcitonin, and raloxifene). Biochemical Bone Turnover Markers have been shown to accurately predict bone density and treatment efficacy while helping document patients' compliance with treatment.
N-Telopeptides and C-Telopeptides (NTx and CTx) are protein fragments of type 1 collagen, making up nearly 90% of the organic portion of bone. These proteins' C- and N-terminals are crosslinked to provide the bone strength needed. When bone is absorbed, CTx and NTx are released into the bloodstream and excreted in the urine. The serum levels of these fragments have been shown to correlate very well with their corresponding urine measurements, of course, when creatinine clearance is co-evaluated. The measurement of these fragments can be used to evaluate treatment response (within 3 to 6 months) and are good indicators of bone resorption.
Biochemical Bone Turnover Markers cannot estimate the risk of bone fracture like bone density can. However, they are essential in evaluating the effectiveness of osteoporosis treatment.
Biochemical Bone Turnover Markers can also monitor the activity and treatment of bone Paget's disease, hyperparathyroidism, and bone metastases. Biochemical Bone Turnover Markers are usually high in children because of the increased bone resorption associated with the development and remodeling of the long bones. Their levels peak around 14 and then gradually decline to adult values. Because estrogens are a potent inhibitor of osteoclast activity (bone resorption), bone loss begins shortly after menopause begins. Therefore, the levels of biochemical markers increase after menopause.
What Do Pathological Values Mean?
- Increase: Osteoporosis, Paget's disease of bones, advanced bone tumors (primary or metastatic), acromegaly, hyperparathyroidism, hyperthyroidism.
- Decrease: Hypoparathyroidism, hypothyroidism, cortisone therapy, effective osteoporosis treatment
The CTx Telopeptide Urine test is no longer performed. Please select the Deoxypyridinoline (DPD) Urine test instead.
