Osteoporosis can be treated with medication. But when a medication targets your bones, how do you know that it’s working?
I’ve seen many patients with osteoporosis who were wondering the same thing. The main way to monitor a person’s response to osteoporosis treatment is with bone density testing. But some patients ask about an additional measure of bone health: bone turnover markers (BTM).
While they’re certainly not always called for, these markers can provide helpful information about the state of your bones in some cases.
What is osteoporosis?
Osteoporosis is a bone disorder characterized by low bone mass and decreased structural integrity of the bone, increasing your risk of fracture. Commonly, osteoporosis is diagnosed based on results from imaging called dual-energy X-ray absorptiometry (DXA). This test is a type of X-ray that can help measure your bone density and, with repeated testing, bone loss over time.
The United States Preventative Task Force, a group of experts who provide direction in prevention and evidence-based medicine, recommends screening all women 65 years and older for osteoporosis. Screening often starts earlier for women with risk factors for bone loss.
A bone mineral density significantly below average is one way to diagnose osteoporosis. With a diagnosis of osteoporosis, your healthcare team may advise you to begin medical treatment. The most common initial medications for osteoporosis are in the drug class called bisphosphonates. These medications work to prevent the breakdown of bone.
One particularly important aspect of treating osteoporosis is monitoring how your bones respond to therapy to ensure that the treatment is working. Traditionally, this is done with regular DXA scanning. In many circumstances, your healthcare team may recommend repeating DXA every 1 to 3 years to monitor for improvement, stability or a slower rate of loss in bone density while on treatment.
An additional consideration for monitoring response to osteoporosis therapy, other than DXA scanning, are bone turnover markers (BTMs). These are not routinely measured, and in many cases may not be necessary. Through shared decision-making with your healthcare team, you can determine if bone turnover markers would be helpful for you.
What are bone turnover markers?
Bones are continually being remodeled inside of the body. Specialized cells in the bone lay down new bone, while other cells break down old bone. This results in various products of the remodeling process being released to the bloodstream, some of which we can measure. These components are called bone turnover markers. Depending on the specific marker measured, they can give your healthcare team a sense of the rate at which old bone is being removed, as well as the rate at which new bone is being formed.
Some common BTMs used to measure bone resorption include C-terminal telopeptide of type 1 collagen (CTX), which is a blood test, as well as urinary N-telopeptide of type 1 collagen (NTX). When these markers are elevated, it suggests that bone is being broken down more quickly.
Among others, N-terminal propeptide of type 1 collage (PINP) is an example of a blood test used to measure bone formation. When elevated, it suggests bone formation is happening at a faster rate.
How can BTMs be used in osteoporosis?
As mentioned, the most common medication class used to treat osteoporosis is bisphosphonate therapy. These drugs work to decrease bone breakdown. That means markers that measure the rate of bone removal should be decreased if the medication is being taken correctly, working appropriately and your bones are responding to therapy.
When treating osteoporosis with bisphosphonates, healthcare professionals may elect to obtain baseline BTMs prior to starting treatment and again 3 to 6 months into treatment to see if the medication is suppressing bone breakdown. A significant decrease in bone resorption markers (like CTX or NTX) would indicate that your bones are responding to the medication. This information could then be used to determine if the medication you are on is working, or if how you take it should be changed.
Notably, these markers do not aid in diagnosing osteoporosis, and are typically only used once a diagnosis has already been established.
How accurate are bone turnover markers?
One drawback of BTMs is that they can vary based on the time of day they are drawn. Eating can also affect the test results. And certain medications as well as supplements can interfere with the test results.
That means BTMs can be hard to reliably track if not done correctly. It is especially important that they are collected in a consistent and standardized way. Typically, BTMs are measured in the morning when fasting. Additionally, it is often suggested you have all measurements done at the same laboratory as various laboratories can have inconsistencies between them.
Are bone turnover markers a good idea for me?
Osteoporosis is a common concern, and it’s important to make sure treatment for the condition is working. While this is typically done with bone density testing, BTMs are a relatively simple lab test that can provide information about the health of your bones. While certainly not required, for some BTMs can provide more data to determine whether or not a treatment is working. Talk to your healthcare team to discuss whether BTM measurements are a good idea for you.
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