Cortisol, Insulin, Cholesterol, & Bones: Understanding Key Health Markers

Maintaining good health involves keeping track of various biomarkers that reflect how our body is functioning. Hormones like insulin and cortisol, as well as blood lipids like cholesterol, are key indicators of metabolic and cardiovascular health. At the same time, our bone density testing results reveal the strength of our skeleton, which is just as crucial for long-term wellness. In this comprehensive guide, we’ll explore what these health markers mean, why they matter, and how tests help in measuring bone strength and overall health status. By understanding these markers, you can take informed steps to improve your well-being and catch potential issues early.

Types of Bone Health Markers

Bone formation markers reflect the anabolic (building) phase of bone remodeling, providing insights into the activity of osteoblasts. These markers are particularly valuable for monitoring the effectiveness of treatments aimed at increasing bone density, such as anabolic therapies for osteoporosis.

• Procollagen Type 1 N-Terminal Propeptide (P1NP): Often considered the gold standard among bone formation markers, P1NP is a byproduct released during the synthesis of type 1 collagen, the primary protein component of bone. As osteoblasts actively lay down new collagen matrix, P1NP is cleaved and released into the bloodstream. Elevated P1NP levels indicate increased osteoblast activity and robust bone formation. Its stability and consistency make it a preferred marker for assessing the response to anabolic treatments and for monitoring overall bone formation rates.
• Bone-Specific Alkaline Phosphatase (BSAP): BSAP is an enzyme produced by osteoblasts that plays a crucial role in the mineralization process of new bone matrix. It facilitates the deposition of calcium and phosphate crystals, essential for hardening bone tissue. Increased levels of BSAP signify heightened osteoblast activity and active bone mineralization. While general alkaline phosphatase can be elevated due to liver issues, the bone-specific isoenzyme provides a more precise measure of bone formation.
• Osteocalcin: This protein is secreted by osteoblasts specifically during the bone formation process. Osteocalcin binds to calcium and is incorporated into the bone matrix, playing a role in its mineralization and strength. Higher circulating levels of osteocalcin are indicative of active bone-building, making it a useful marker for assessing osteoblast function and bone turnover.

Bone resorption markers, on the other hand, indicate the catabolic (breaking down) phase of bone remodeling, reflecting the rate at which osteoclasts are dissolving old bone tissue. Elevated levels of these markers can signal accelerated bone loss and an increased risk of fractures.

• C-terminal Telopeptide of Type 1 Collagen (CTX): This is the most commonly used and clinically relevant bone resorption marker. CTX is a fragment released into the bloodstream when osteoclasts break down mature type 1 collagen fibers in bone. As collagen is degraded, its cross-linked peptides, including CTX, are released. High CTX levels suggest an increased rate of bone breakdown, which can be indicative of conditions like osteoporosis, hyperparathyroidism, or other bone-losing disorders. Monitoring CTX levels can help assess the effectiveness of anti-resorptive therapies, such as bisphosphonates, in reducing bone loss.
• N-terminal Telopeptide of Type 1 Collagen (NTX): Similar to CTX, NTX is another fragment of type 1 collagen released during bone degradation. It can be measured in either blood or urine and serves as another valuable indicator of collagen breakdown by osteoclasts. Elevated NTX levels also point towards increased bone resorption activity.
• Deoxypyridinoline (DPD): DPD is a stable cross-link compound that connects collagen molecules, providing structural integrity to bone. When bone is broken down, DPD is released and excreted in the urine. Increased urinary DPD levels are a direct reflection of heightened bone collagen degradation and osteoclast activity.
• Tartrate-Resistant Acid Phosphatase (TRAP): TRAP is an enzyme predominantly produced by osteoclasts. It plays a role in the breakdown of bone matrix. While less commonly used in routine clinical practice compared to CTX or NTX, elevated TRAP levels specifically indicate increased osteoclast numbers and activity, providing a direct measure of bone resorption.

Monitoring both bone formation and resorption markers allows clinicians to assess the dynamic balance of bone remodeling. An imbalance, where resorption outpaces formation, can lead to conditions like osteoporosis, characterized by weakened bones and increased fracture risk.

Interpretation of Test Results

Interpreting bone health marker results requires understanding not only the absolute values but also the context in which tests are performed. For example, a high level of C-terminal telopeptide of type 1 collagen (CTX) generally indicates increased bone breakdown. This can be seen in conditions such as osteoporosis, hyperparathyroidism, or in individuals experiencing rapid bone loss. Conversely, a low CTX level suggests slower bone resorption, which may be desirable during antiresorptive therapy. Procollagen Type 1 N-Terminal Propeptide (P1NP), a bone formation marker, reflects the activity of osteoblasts. Elevated P1NP levels suggest increased bone formation, which can occur during anabolic treatment or in the healing phase after a fracture. Low P1NP may indicate suppressed bone formation, which could be due to aging, certain medications, or underlying diseases.

It’s crucial to recognize that various physiological and external factors influence bone marker levels. Time of day is significant—markers like CTX exhibit significant diurnal variation, peaking in the early morning and declining throughout the day, so samples are best collected in the morning after fasting. Food intake can also affect results, as can age, sex, menopausal status, and renal function. For example, impaired kidney function can cause certain markers (like P1NP) to accumulate, leading to falsely elevated readings.

The most meaningful information often comes from tracking trends in marker levels over time rather than relying on a single measurement. For patients undergoing osteoporosis treatment, a significant decrease in bone resorption markers (such as CTX) or an increase in bone formation markers (such as P1NP) within three to six months typically indicates a favorable response to therapy. Lack of change or unexpected results may prompt further investigation into medication adherence or secondary causes.

Limitations and Considerations of Bone Health Markers

While bone health markers offer valuable insights into bone metabolism, their clinical application is limited by several key factors. One key limitation is biological variability—marker levels fluctuate naturally due to factors such as age, sex, hormonal status, diet, and even the time of day. Markers such as CTX exhibit significant diurnal variation, requiring samples to be collected consistently in the morning after fasting. Assay differences also pose challenges: results can vary between different laboratories or testing methods, making it critical to use the same assay and laboratory for serial measurements. Preanalytical factors, such as sample handling, timing, and whether the marker is measured in serum or urine, further contribute to variability. Urine markers, for instance, are more susceptible to changes in kidney function and hydration status, while serum markers tend to be more stable and easier to interpret. Analytical variability—differences in how tests are performed or calibrated—can also affect results. Importantly, bone health markers are not recommended for general population screening, as many non-disease factors can influence their levels and do not provide a definitive diagnosis. These limitations mean that interpreting bone marker results requires caution and consideration of the clinical context; trends over time are often more meaningful than single measurements, and results should always be considered in conjunction with other clinical and imaging findings.

Testing Procedures and Sample Collection

These tests typically require either a blood or urine sample, depending on the specific marker being evaluated. For most bone formation markers, a blood sample is collected by inserting a needle into a vein, usually in the arm. Bone resorption markers, including the C-terminal telopeptide of type 1 collagen (CTX) and the N-terminal telopeptide (NTX), can be measured in either blood or urine. For urine-based tests, a random or timed urine sample is collected in a sterile container provided by the laboratory. In some cases, the test may require a specific urine collection, such as the second morning void, to ensure consistency.

Proper preparation is crucial for obtaining accurate results from bone health marker tests. Many of these markers, particularly CTX, exhibit significant diurnal variation—meaning their levels fluctuate throughout the day. As a result, healthcare providers typically recommend collecting samples in the early morning, after an overnight fast, to minimize variability. Fasting is essential because food intake can temporarily alter the concentration of some markers, potentially leading to misleading results. For urine samples, following the laboratory’s instructions on timing and collection method is essential. Additionally, it is best practice to have repeat tests performed at the same time of day and, if possible, at the same laboratory, as different testing methods and instruments can yield slightly different results. By adhering to these standardized procedures, clinicians and patients can ensure that bone health marker measurements are reliable and comparable over time, providing valuable insights into bone metabolism and the effectiveness of treatment strategies.

Insulin and Blood Sugar: Metabolic Health Markers

Insulin is a hormone produced by the pancreas that helps regulate blood sugar levels by allowing cells to absorb glucose from the bloodstream. It’s central to how our body uses energy. Doctors often check blood sugar markers, such as fasting glucose and hemoglobin A1c, to determine if insulin is functioning correctly. When insulin’s effects start to falter, a condition called insulin resistance can develop. In insulin resistance, the cells in muscle, fat, and liver become less responsive to insulin, resulting in blood sugar levels remaining higher than normal. The body may compensate by producing more insulin for a while, but over time this can lead to prediabetes or type 2 diabetes if not addressed.

Recognizing Insulin Resistance Signs

One challenge is that insulin resistance often develops silently. Many people won’t notice obvious symptoms at first. However, there are some telltale insulin resistance signs that physicians look for during checkups. These include visible skin changes, such as skin tags or patches of darkened, velvety skin, especially around the neck or armpits, as well as unexplained weight gain or difficulty losing weight. A large waist circumference is another red flag that often accompanies insulin resistance. High blood pressure and high triglycerides (a type of blood fat) often co-occur with low HDL (“good”) cholesterol, which is also commonly associated with insulin resistance, as part of metabolic syndrome. Individually, each of these signs might not be obvious, but together they paint a picture of a metabolism under strain.

From a laboratory perspective, early insulin resistance may be indicated by a slightly elevated fasting blood sugar (above ~100 mg/dL) or an HbA1c level in the prediabetes range (5.7–6.4%). The pancreas is working overtime to regulate blood glucose levels, so insulin levels in the blood can be higher than normal. If a doctor suspects insulin resistance, they may order an oral glucose tolerance test or check fasting insulin levels to determine how well your body handles sugar. Identifying insulin resistance early is essential because it’s reversible with lifestyle changes like improved diet, regular exercise, and weight loss. By managing these blood sugar markers and addressing insulin resistance promptly, you can significantly reduce the risk of developing type 2 diabetes and related complications.

Cholesterol: A Key Indicator of Heart Health

Cholesterol is a waxy fat-like substance found in your blood. It’s essential for building cells and producing certain hormones, but having too much of the wrong type of cholesterol can increase your risk of heart disease. When you get a lipid panel blood test, it typically reports several important values: LDL (low-density lipoprotein), HDL (high-density lipoprotein), total cholesterol, and triglycerides. LDL is often referred to as “bad” cholesterol because high levels of LDL can contribute to plaque buildup in arteries, whereas HDL is known as “good” cholesterol, as it helps remove cholesterol from the bloodstream.

Monitoring cholesterol levels is a routine part of assessing cardiovascular health. High cholesterol is prevalent – globally, raised total cholesterol affects roughly 39% of adults. In the United States, millions of people have cholesterol levels above recommended limits. Because high cholesterol itself usually has no symptoms, it’s essential to get it checked with a blood test. Blood sugar markers and cholesterol often go hand in hand, as conditions like diabetes or insulin resistance can negatively impact your cholesterol profile.

Understanding Your Cholesterol Numbers

A healthy total cholesterol level is generally considered to be below 200 mg/dL, with LDL ideally below 100 mg/dL for most individuals (lower if one has risk factors or heart disease) and HDL above 40 mg/dL in men and 50 mg/dL in women. Doctors pay special attention to LDL because it’s a primary driver of atherosclerosis (hardening and narrowing of the arteries). If your LDL is high or your HDL is low, your doctor may recommend lifestyle changes like diet and exercise, and possibly medications such as statins to lower your risk of heart attack and stroke.

In addition to absolute numbers, physicians consider your overall risk profile. This includes factors like age, family history of heart disease, smoking status, blood pressure, and the presence of diabetes or insulin resistance signs. All these factors together, including your cholesterol levels, give a better picture of your cardiovascular risk than any single number. By keeping cholesterol in check through a healthy diet (low in saturated and trans fats), regular physical activity, and medications when necessary, you can significantly reduce your chances of cardiovascular problems down the line.

Cortisol: The Stress Hormone and Its Impact

Whereas insulin and cholesterol are measured to assess metabolic and heart health, cortisol is a hormone that serves as a marker of stress and adrenal function. The adrenal glands produce cortisol and are often called the “stress hormone” because their levels rise in response to stress. It plays a vital role in many bodily processes, helping to regulate blood pressure, reduce inflammation, and control how the body metabolizes fats, proteins, and carbohydrates. Cortisol follows a daily cycle, typically peaking in the early morning to help you wake up and gradually declining throughout the day.

In short bursts, cortisol is beneficial and part of a healthy response. However, problems arise when cortisol levels remain elevated chronically, as can occur with ongoing stress or certain medical conditions. Cortisol in excess over long periods can wreak havoc on the body. Chronically high cortisol levels can lead to weight gain (especially fat around the abdomen), disrupted sleep or insomnia, mood swings or anxiety, and even weaken your bones. Too much cortisol for too long can contribute to a loss of bone density and muscle mass. People with Cushing’s syndrome, a condition of very high cortisol, usually experience brittle bones, high blood sugar, and high blood pressure.

On the flip side, abnormally low cortisol (as in Addison’s disease or adrenal insufficiency) can cause fatigue, weight loss, low blood pressure, and other issues. However, low cortisol conditions are less common than high cortisol states. For most people, the primary concern is managing stress to maintain cortisol levels within a healthy range. Techniques such as regular exercise, meditation, adequate sleep, and relaxation practices can help maintain cortisol’s daily cycle in balance. If you have symptoms of chronically high cortisol – persistent belly weight gain despite diet, severe fatigue, high blood sugars, or bone loss – doctors can test your cortisol with blood, urine, or saliva tests. Keeping cortisol under control not only helps you feel better day to day, but also protects your long-term health.

Bone Density: A Vital but Overlooked Health Marker

When thinking about health metrics, people often focus on blood tests and hormones, but skeletal health diagnostics are equally important, especially as we age. Bone health is typically assessed by measuring bone mineral density (BMD) – essentially the concentration of minerals (like calcium and phosphorus) in your bones. Strong bones are crucial for mobility and overall quality of life, and low bone density can lead to osteoporosis, a condition in which bones become weak and fragile. Unfortunately, osteoporosis is often called a “silent” disease because you won’t know your bones are thinning until a fracture happens, unless you actively check your bone density.

What is Bone Mineral Density?

Bone mineral density is measured in grams of mineral per cubic centimeter of bone. Still, you don’t need to remember the units – what’s important is how your BMD compares to healthy standards. Fundamentally, BMD reflects mineral levels in bones. In fact, human bones serve as a major mineral reservoir for the body. Approximately 99% of the calcium in your body is stored in your bones, along with about 85% of your phosphorus and over half of your magnesium and sodium. This mineral content is what gives bones their rigidity and strength. So when we measure “bone density,” we’re basically measuring how packed those minerals are in a section of bone.

The results of a bone density test are usually given as a T-score. This is a comparison of your bone density to that of a healthy 30-year-old adult (peak bone mass age). A T-score of 0 means your bone density is equal to the norm for a healthy young adult. If your T-score is above 0, that means your bones are denser than average; if it’s negative, your bones are less dense. According to World Health Organization (WHO) criteria, a T-score above -1 is considered normal bone density. A T-score between –1.0 and –2.5 is classified as osteopenia (meaning lower than normal bone density, but not yet osteoporosis). A T-score of –2.5 or below indicates osteoporosis. These bone density indicators help doctors determine if you need to take steps to protect your bones, such as taking calcium/vitamin D, starting medications, or making lifestyle changes. The report may also include a Z-score, which compares your bone density to what’s typical for someone of your age and gender.

Why Bone Density Matters

Healthy bones protect internal organs and house our bone marrow. Low bone density means your bones have less mineral content than they should, and this correlates with reduced bone strength. People with osteoporosis have bones that can fracture from relatively minor stresses. That’s why osteoporosis screening is recommended for all women by age 65 and for men by age 70, or sooner if at high risk. Early detection of low bone density via a bone density scan can be life-saving – a hip fracture in an older adult, for example, can lead to severe complications. Knowing your bone density allows you to take preventive action (medications, weight-bearing exercise, nutrition) to strengthen your bones and reduce fracture risk.

DEXA Scans: The Gold Standard for Bone Health Assessment

The DEXA Scan Procedure and What to Expect

It is straightforward and non-invasive. You lie down on a padded table, and the DEXA machine’s scanning arm passes over your body. It’s not claustrophobic like an MRI. The machine is open, and the arm moves above you. Typically, the focus is on the lower spine and hips, as these sites provide a strong indication of overall fracture risk and are common areas for osteoporosis-related fractures. You’ll be asked to stay still and breathe normally while the scanner does its work. The amount of X-ray radiation used in a DEXA is extremely low – much lower than a standard chest X-ray or CT scan. There are no injections, no contrast dyes, and you don’t even need to change into a gown as long as your clothes don’t have metal zippers or buttons. In short, as far as medical tests go, it’s an easy and comfortable experience. The machine will produce images and data that the software then uses to calculate your bone density at each scanned site.

What makes DEXA particularly useful is not just its ease, but its precision. DEXA scans have very high accuracy and repeatability for measuring BMD. The DEXA scan is considered the gold standard or most accurate test for assessing bone density. DEXA scan accuracy is high enough to detect even small changes in bone density over time. This is why if you’re on osteoporosis treatment, your doctor might have you repeat a DEXA every 1-2 years to see if your bone density is improving.

DEXA for body composition and bone strength

While DEXA was initially developed to assess bone health (and remains the diagnostic imaging method for bone loss and osteoporosis), it has an additional capability: it can measure body composition. During a full-body DEXA scan, the machine can distinguish between bone, lean tissue (muscle), and fat tissue across your body. The result is a detailed breakdown of your body fat percentage, lean mass, and bone mass for different regions. This means a DEXA body scan provides insights not only into bone strength but also into your overall fitness and muscle-to-fat balance. For athletes or individuals on weight loss programs, DEXA offers a far more precise analysis of body composition than standard methods, such as bioelectrical impedance scales or skinfold calipers.

It’s worth noting that when it comes to measuring bone strength, what we’re really measuring is bone density as a proxy for strength. Bone strength in the absolute sense also depends on bone quality factors (like the microarchitecture of the bone and the rate of bone turnover), which DEXA doesn’t directly measure. However, bone density correlates strongly with strength – a denser bone is usually a stronger bone.

Given DEXA’s capabilities, many people are now getting scans not just at hospitals, but also at fitness centers or clinics, as part of their general health assessments. For example, some specialized wellness services like BOD offer DEXA scans that provide both bone density results and a full body composition analysis in one sitting. These scans can help you track progress in fat loss or muscle gain programs, while also monitoring your bone health. DEXA’s versatility in assessing both bone density indicators and body composition makes it a standout tool in personal health monitoring.

Other Methods of Bone Density Testing

DEXA is the most widely used method for measuring bone density, but it’s not the only way. There are a few skeletal health diagnostics available as alternatives or supplements, each with its pros and cons. It’s helpful to be aware of them, especially if a DEXA scan isn’t immediately available.

1. Quantitative Computed Tomography (QCT): QCT uses a specialized CT scan (CAT scan) to measure bone density, typically in the spine. It provides a true three-dimensional assessment of bone, which can separate the spongy inner bone (trabecular bone) from the harder outer bone (cortical bone) in its analysis. QCT can be more sensitive in certain situations – for example, it may detect changes in trabecular bone sooner, and it’s less affected by spinal arthritis or calcifications than DEXA results. However, QCT involves a higher dose of radiation than DEXA and is less commonly available. It’s also more expensive and lacks the huge database of population norms that DEXA has. Doctors may use QCT if a DEXA scan is inconclusive or if there’s a specific reason to obtain that 3D detail; however, for routine osteoporosis screening, DEXA is usually preferred.
2. Quantitative Ultrasound (QUS): Ultrasound can also be used to estimate bone density. This is usually done at the heel (calcaneus) using a portable ultrasound device. The test measures how sound waves travel through the bone, indicating bone density and structure. The big advantage here is that it’s quick, radiation-free, and often low-cost – you might encounter heel ultrasound screenings at health fairs or pharmacies. The downside is that it doesn’t directly measure the same thing as a DEXA, and it only checks one site (the heel), which isn’t a common fracture site like the hip or spine. While a heel ultrasound can be a convenient imaging tool for screening bone loss, it cannot definitively diagnose osteoporosis. Many people with low heel ultrasound scores will go on to get a full DEXA scan for confirmation.
3. Peripheral DEXA and other portable scanners: In addition to the central DEXA machines used for spine and hip, there are smaller devices that measure bone density at peripheral sites like the forearm, wrist, or finger. Some doctor’s offices or clinics use these for a quick check. There are also older methods, such as radiographic absorptiometry (an X-ray of the hand that estimates bone density) or single-energy X-ray absorptiometry (SXA), which were historically used for forearm measurements. These methods are generally less accurate and less predictive of fracture risk than a central DEXA scan. They might be used when a full DEXA isn’t available, or for certain research purposes, but they aren’t the main tools for diagnosis.

It’s clear that while these other methods can provide some information, they have limitations. Alternative bone tests can measure bone density to some degree, but they are typically used only as preliminary screenings since they lack the precision and comprehensive data of a DEXA scan.

Accessibility and Cost of a DEXA scan

The cost of this imaging for bone loss can vary significantly depending on the location and whether your insurance covers it. In medical settings, if your doctor orders a DEXA for osteoporosis risk assessment, insurance will usually cover it (for example, Medicare in the U.S. covers bone density screening every two years for women over 65 or others at risk). Out-of-pocket prices for a DEXA scan range from relatively inexpensive (perhaps around $50–$150 at a dedicated DEXA clinic or during a health fair event) to a few hundred dollars at major hospitals. On average, the DEXA scan price in the U.S. is roughly in the few hundred-dollar range if paid by yourself, with one analysis noting an average above $300 for hospital-based DEXA tests. Fortunately, for those who meet screening guidelines or have a medical need, health insurance often covers it entirely or with a minimal co-pay, so be sure to check with your provider.

When scheduling a DEXA scan bone density, ask if the price quoted is all-inclusive. In some medical facilities, there might be a separate charge for the radiologist to interpret the scan. However, many places (especially outpatient imaging centers or wellness providers) give a single price that includes the full report. The procedure doesn’t take long, so you’re typically in and out fairly quickly. Considering the wealth of information a DEXA scan provides and its role in preventing severe fractures, the investment in this test is well worth it. And if cost is a concern, keep an eye out for community osteoporosis screening events – local hospitals or public health organizations sometimes offer free or low-cost bone density checks. While these tests may not be as definitive as DEXA, they can at least indicate if further testing is warranted.

Understanding and monitoring key health markers is a cornerstone of preventive healthcare. Hormones like insulin give insight into our metabolic health – catching insulin resistance signs early can help ward off diabetes. Cholesterol levels reveal cardiovascular risk and guide us in preventing heart disease. The stress hormone cortisol reminds us that managing stress is not just about peace of mind, but also about physical health, since chronically high cortisol can trigger weight gain, high blood pressure, and even bone loss. And speaking of bones, knowing your bone density is vital as you age; it’s an often overlooked part of health that has enormous implications for your mobility and independence later in life. Thanks to bone density testing tools like the DEXA scan, we can assess our bone strength before a fracture occurs. The DEXA scan stands out among skeletal health diagnostics for its accuracy and additional benefits, making it a valuable addition to your health regimen.

Sources:

• Cleveland Clinic – Insulin Resistance: What It Is, Causes, Symptoms & Treatmentmy.clevelandclinic.org
• World Heart Federation – High Cholesterol & Cardiovascular Healthworld-heart-federation.org
• Torrance Memorial Healthy Living – Cortisol and Your Waistline: The Unseen Battletorrancememorial.org
• Medical News Today – What to know about bone density testingmedicalnewstoday.com
• Johns Hopkins Medicine – Bone Densitometry (Bone Density Test) Overviewhopkinsmedicine.org
• Northern Arizona Radiology – DEXA and Bone Density QCTnorthernarizonaradiology.com
• GoodRx – What Is a DEXA Scan? Procedure, Results, and Costgoodrx.com