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Are you having bone loss? How can bone resorption assessment play a role in diagnosis?

There is continuous re-absorption of your old bone and creation of new bone throughout your life time. Your bones stay strong as long as there is balance between bone formation and re-absorption. Bone loss occurs when there is more re-absorption of the old bone than the creation of new bone.  When this process of bone loss reaches a certain stage, it is called osteoporosis. There are several causes of osteoporosis which we will review here.

Causes of bone loss

It is essential for you to know what is causing your bone loss. Bone loss can occur without any known cause or it can run in families when the condition is inherited. Age is a major factor for bone loss which should be considered since women over age 50 and men over age 70 have a higher risk of osteoporosis than younger women and men due to the drop in their hormone levels. Your lifestyle and habits are also related to bone loss. Your body may not make enough new bone if you do not eat enough high-calcium foods or when your body does not absorb enough calcium from the foods you eat. Habits such as drinking excessive alcohol and smoking lead to weaker bones and increases your risk for fractures.

In addition, several long-term medical conditions can keep you sedentary, preventing normal function of muscles and bones which leads to bone loss. Other medical conditions which may also lead to bone loss are: Rheumatoid arthritis, chronic kidney disease, overactive parathyroid gland, conditions causing malabsorption from small intestine, eating disorders such as anorexia nervosa or bulimia. There are medicines which can cause osteoporosis such as hormone-blocking treatments for prostate cancer or breast cancer, glucocorticoid (steroid) medicines and anti-seizure medications.


How is bone resorption measured?

Your doctor will order bone resorption assessment when you are having bone loss. In this test, the components of your bone collagen which include pyridinoline (PYD) and deoxypyridinoline (DPD) are assessed in your urine sample. Pyridinoline (PYD) indicates collagen loss of all types and its component deoxypyridinoline (DPD) particularly reflects bone collagen. During the process of bone resorption, the crosslinked collagens are broken down by protein releasing enzymes and then the DPD is released into the circulation and excreted by urine. Likewise, PYD is also released into circulation and excreted in urine following degradation of collagen in bones, ligaments and cartilages.


Benefits of Bone Resorption Assessment

  • The method of measuring urinary bone resorption is easy, inexpensive and dynamic measure of bone turnover.
  • It is a quick method to know the rate of bone loss, thus assisting to predict future losses unlike static markers of bone mass, such as bone scans which diagnose osteoporosis by measuring the amount of bone that has already been lost, not giving data on the rate of loss.
  • It is a non-invasive method of measuring bone resorption which can indicate the need for early and preventive strategies for development of further bone loss.
  • It is also applied for monitoring of therapy for bone resorption and can indicate the effectiveness of intervention in treatment of bone loss.


Relationship of bone resorption markers to bone loss

Conditions of bone loss – Lets see how conditions of bone loss are related to bone markers in general

Osteoporosis – In case, you are an elderly woman having osteoporosis with fractures, you have high levels of bone resorption markers, PYD and DPD in your urine.  Patients with recent fractures showed higher excretion of both markers than those without recent fractures, indicating that accidental bone fractures also increase crosslink excretion. Similarly, if you are a postmenopausal woman with a high rate of bone of bone turnover, it indicates that bone loss is likely rapid. Approximately all women will show high bone turnover in the first few years after menopause, but about a third will continue to have high turnover 10-20 years after menopause.

Other bone related conditions – The urinary excretion of both markers is highly elevated in case you are having bone loss associated with disorders such as Paget’s disease, primary hyperparathyroidism, osteomalacia or cancers.

Bone resorption markers – Lets see how bone markers are specifically related to bone loss

Pyridinoline - The levels of Pyridinoline cross links is elevated in conditions affecting bone, cartilage and connective tissue. For instance, levels are elevated if you have conditions related to connective tissue such as Rheumatoid arthritis, bone conditions such as osteoarthritis and bone loss due to chronic alcohol ingestion. Hence, it is a non-specific bone marker.

Deoxypyridinoline - When levels of Deoxypyridinoline are elevated, it points out that you have increased bone loss. Even when you don’t have any underlying bone disease, it is an important marker in the development and progress of osteoporosis. Recent fracture or a rapid rate of bone turn over is suggested by the elevated levels. It is the most specific marker of bone loss.

Discuss with your physician about your risk for bone loss and osteoporosis. He /she will determine your requirement for bone resorption assessment and further testing. You can find out how to get the right amount of calcium and vitamin D, what exercise or lifestyle changes are right for you and what medicines you may need to take once the diagnosis has been established by your physician. Thus, bone resorption assessment plays a vital role in management of your bone loss.