Why is my bone density so high? Causes and concerns

While osteoporosis—the loss of bone density—is a well-known concern, an unusually high bone mineral density can also be a significant finding. Discover the surprising reasons behind a high DEXA scan result and learn why is my bone density so high and if it warrants further investigation.

Quick Summary

Higher than normal bone density can result from a variety of causes, ranging from benign conditions like arthritis to more serious underlying disorders, genetic factors, or even medication side effects. While sometimes a sign of stronger bones, in other cases, elevated density can point to underlying issues that need medical attention.

Key Points

• DEXA Results Can Be Misleading: A high bone density reading on a DEXA scan, especially in older adults, can often be an artificial result caused by factors like spinal arthritis or vascular calcification, which can obscure an accurate reading.

• Underlying Medical Conditions: Generalized high bone mass can be a sign of systemic illnesses such as renal osteodystrophy, certain cancers, or rare genetic disorders like osteopetrosis and sclerosteosis.

• Genetics Play a Role: Rare genetic mutations, such as those affecting the LRP5 or SOST genes, are known to cause inherited high bone mass, leading to exceptionally dense bones.

• High Bone Density Isn't Always Strong: Paradoxically, some conditions that cause very high bone density, like osteopetrosis, result in bones that are brittle and more prone to fracture, demonstrating that density does not always equate to strength.

• Comprehensive Medical Evaluation is Needed: If you receive a high bone density diagnosis, a detailed medical history, careful scan review, and possibly additional tests are necessary to distinguish between a benign finding and a more serious underlying pathology.

• High Weight-Bearing Activity can Increase Density: High levels of weight-bearing exercise and higher body weight are benign, common causes for increased bone mineral density.

Understanding Bone Mineral Density (BMD) and DEXA Scans

Bone mineral density (BMD) is a measure of the amount of bone mineral per unit volume or area. It is most commonly measured using a dual-energy X-ray absorptiometry (DEXA or DXA) scan. For most people, the concern is low bone density (osteoporosis), which increases the risk of fractures. However, an exceptionally high BMD, indicated by a Z-score significantly above the norm, is not always a positive finding and may require further evaluation. A Z-score compares your bone density to that of other people of your same age and sex. A Z-score greater than +2.5 can be considered high and is a trigger for a doctor to look for other causes.

Common causes of unexpectedly high bone density

When a DEXA scan reveals high bone density, the causes can be categorized into a few main areas:

Artefactual or localized causes

Often, a high DEXA reading is not a true representation of strong, healthy bone but rather an artifact caused by other conditions. This is one of the most common reasons for a deceptively high bone density measurement, particularly in older individuals.

• Degenerative spinal changes: Osteoarthritis and degenerative disease of the spine are very common, especially in aging adults. The extra bone growth and calcification from these conditions can lead to an artificially high bone density reading, particularly in the lumbar spine.
• Vascular calcification: Calcified plaques in the abdominal aorta and other blood vessels near the spine can be picked up by the DEXA scan and inflate the measured bone mineral density.
• Prior medical procedures: Implants, such as vascular prostheses or material from a vertebroplasty, can also lead to an artificially high reading.
• Paget's disease: This chronic bone disorder is characterized by excessive bone formation and resorption, leading to disorganized and weakened bone structure that appears dense on a scan. It can affect one or several bones.

Acquired systemic conditions

Some medical conditions can cause a generalized increase in bone mass throughout the skeleton. These are less common than artefactual causes but are important to diagnose.

• Renal osteodystrophy: This condition can develop in individuals with chronic kidney disease and is linked to the body's mineral and hormone imbalance. It can sometimes lead to sclerotic bands in the vertebrae that appear as a high bone density pattern.
• Certain types of malignancy: Some cancers, such as prostate cancer, can metastasize to the bone and cause an increase in bone formation, which increases bone density.
• Fluorosis: Excessive intake of fluoride, which can occur from water or other sources, can lead to diffuse bone sclerosis.
• Hepatitis C-associated osteosclerosis: A rare condition where Hepatitis C infection is associated with diffuse bone density increases.
• Mastocytosis: This disorder involves an overproduction of mast cells, which can sometimes result in increased bone density.

Rare genetic disorders

In rare instances, high bone density is caused by inherited disorders that affect bone formation or resorption. These are often present from birth and are part of a broader syndrome.

• Osteopetrosis: A group of rare genetic disorders that cause bones to harden and become abnormally dense. This is due to a malfunction in osteoclasts, the cells that break down old bone.
• Sclerosteosis and van Buchem disease: These are rare conditions caused by mutations in the SOST gene, which encodes sclerostin, a protein that inhibits bone formation. The mutations lead to increased bone mass and can cause neurological problems if the skull thickens too much.
• LRP5 gene mutations: Mutations in this gene can also cause genetic high bone mass phenotypes.

Other factors influencing bone density

• Physical activity and body weight: High levels of weight-bearing exercise and having a higher body weight (due to lean or fat mass) have long been associated with higher bone density. The mechanical stress on the bones stimulates bone growth and remodeling.
• Certain medications: While some medications cause bone loss (e.g., glucocorticoids), others, such as thiazide diuretics, can have a positive effect on bone density by reducing calcium excretion.

What to do if your bone density is high

If your DEXA scan results show an unusually high bone density, it is not a cause for panic, but it is a reason for further investigation by a healthcare professional.

1. Analyze the DEXA scan carefully: A radiologist and your doctor will review the images to determine if the high reading is uniform or if it's localized. They can look for signs of degenerative changes or calcifications that might be causing an artificial reading.
2. Review your medical history: Discuss your full medical history with your doctor. Certain conditions, past surgeries, or long-term medication use may provide clues.
3. Conduct further testing: Depending on the initial evaluation, your doctor may order additional imaging, such as a different type of X-ray or a CT scan, to get a clearer picture of your bone structure. Blood tests to check mineral levels and other markers might also be necessary.
4. Consult a specialist: For complex cases, a referral to a rheumatologist or an endocrinologist who specializes in bone and mineral metabolism may be necessary.

Comparing benign versus pathological causes

It's important to differentiate between benign causes of high bone density and those that are indicative of an underlying issue. A doctor will use a comprehensive approach to determine the root cause. This table provides a basic overview of some differences.

Feature	Benign (e.g., Osteoarthritis)	Pathological (e.g., Osteopetrosis)
Symptom Profile	Often associated with joint pain and stiffness in affected areas.	May present with bone fragility (paradoxically), nerve entrapment, or skeletal abnormalities.
Scan Appearance	High density often localized to specific, affected joints or areas with calcification.	High density is typically uniform and widespread throughout the skeleton.
Fracture Risk	Not necessarily protective. High density due to arthritis can coexist with osteoporosis.	Increased fracture risk due to brittle, abnormal bone structure, despite high density.
Underlying Cause	A common wear-and-tear condition of aging.	A rare genetic or systemic disorder affecting bone metabolism.

The importance of a full medical evaluation

While high bone density is less commonly discussed than low bone density, it's crucial not to dismiss it, especially when it's an unexpected finding. An exceptionally high reading warrants a thorough medical investigation to rule out any serious conditions. Ignoring it could mean missing a timely diagnosis for a treatable underlying disorder, potentially preventing complications. Your doctor is your best resource for interpreting your specific DEXA scan results within the context of your overall health. For further reading on bone health in older adults, visit the National Institute on Aging: https://www.nia.nih.gov/health/bone-health-and-osteoporosis.

Conclusion

High bone density can arise from a variety of causes, from the simple and benign to the rare and serious. Artifacts from age-related degenerative conditions are a frequent cause, but it is crucial not to miss systemic or genetic disorders that could be responsible. Working closely with your healthcare provider to interpret DEXA scan results and, if necessary, pursue further diagnostic tests is the best approach to understanding why your bone density is so high and ensuring your overall bone health.

Frequently Asked Questions

Does high bone density mean I have strong bones?

Not necessarily. While high bone density often indicates strong, healthy bone, certain diseases like osteopetrosis cause bones to become abnormally dense yet brittle and fragile, making them prone to fracture. A full medical evaluation is needed to determine the quality of the bone.

What is a Z-score and how does it relate to high bone density?

A Z-score on a DEXA scan compares your bone density to that of an average person of your same age, sex, and ethnicity. A Z-score significantly above the norm (e.g., > +2.5) is considered high and prompts a deeper investigation into its cause.

Can arthritis cause a high DEXA reading?

Yes, it can. Degenerative joint disease, or arthritis, in the spine or hips can cause extra bone growth and calcification. This makes the bone appear denser on a DEXA scan, artificially elevating the reading, and is one of the most common causes of this finding.

Are there any symptoms of high bone density?

High bone density itself often doesn't cause symptoms. However, if it's due to an underlying condition, you might experience related symptoms, such as bone pain, fatigue, or neurological issues, depending on the cause.

What lifestyle factors can influence high bone density?

Engaging in high-impact, weight-bearing exercise and having a higher body mass index (BMI) can naturally contribute to higher bone density, as the skeleton adapts to greater load.

Is high bone density an urgent medical problem?

While not always an emergency, a finding of unusually high bone density should not be ignored. It requires prompt medical attention and follow-up to ensure that it isn't masking a more serious issue that needs early management.

Can medication increase my bone density?

Some medications, like certain diuretics (thiazides), have a side effect of increasing bone density by affecting calcium excretion. Your doctor will review any medications you take to see if they are a contributing factor.