Does levothyroxine affect your bones? Understanding the complex relationship between thyroid medication and bone health

October 11, 2025 •

3 min read

According to research presented in late 2024, approximately 23 million Americans take levothyroxine daily, and new studies suggest a potential link between its use and bone loss in older adults, even with TSH levels in the normal range. This raises important questions about whether and how does levothyroxine affect your bones and bone health over the long term.

Quick Summary

Levothyroxine's effect on bones depends on dosage and individual factors. Overtreatment can increase bone turnover and density loss, while proper dosage for overt hypothyroidism is generally safe. Recent studies suggest a link to bone loss in some older adults, emphasizing monitoring and personalized risk assessment.

Key Points

Dosage is Crucial: Overtreatment with levothyroxine, resulting in high levels of thyroid hormone, can lead to increased bone turnover and potential bone loss.
TSH Suppression is a High-Risk Scenario: Patients receiving TSH-suppressive doses of levothyroxine for conditions like thyroid cancer have a higher risk of developing osteoporosis and fractures.
Older Adults are More Vulnerable: Recent studies indicate that older adults, including those with TSH levels within the normal range, may experience accelerated bone density loss with long-term levothyroxine use.
Properly Controlled Therapy is Key: When hypothyroidism is well-managed with the correct dose, the risk to bone health is generally minimal and the benefits of treatment outweigh potential risks.
Monitoring is Essential: Regular TSH monitoring allows doctors to adjust levothyroxine dosage to prevent overtreatment and mitigate potential risks to bone health.
Risk Factors Vary: Menopausal status, age, and the severity of the underlying thyroid condition can influence the impact of levothyroxine therapy on bones.

The Dual-Edged Sword: How Thyroid Hormone Impacts Bones

Thyroid hormones are essential for regulating the body's metabolism, including bone remodeling. While crucial for bone development in youth, excessive thyroid hormone can accelerate bone breakdown, leading to bone mass loss. Levothyroxine, a synthetic thyroid hormone, can thus impact bone health, depending on how it's used.

For those with hypothyroidism, levothyroxine aims to normalize thyroid hormone levels. If this balance is maintained, bone health risk is typically low. However, long-term treatment, especially in older individuals or when suppressing TSH for conditions like thyroid cancer, can pose risks.

The Risks of Thyroid Hormone Excess

Taking too much levothyroxine can result in over-replacement, mimicking hyperthyroidism. This overstimulation increases bone turnover and resorption, where old bone breaks down faster than new bone forms. This can reduce bone mineral density (BMD), a risk factor for osteopenia and osteoporosis.

Research highlights key concerns:

TSH Suppression Therapy: High-dose levothyroxine to suppress TSH in patients, such as those with thyroid cancer, is linked to a higher risk of osteoporosis and fractures.
Overtreatment in Older Adults: Chronic overtreatment, even with TSH in the normal range, is associated with a greater fracture risk, particularly in older postmenopausal women. Some studies suggest many long-term levothyroxine patients may be over-replaced.
Findings in Euthyroid Patients: A recent study in older, euthyroid adults on levothyroxine suggested a link between long-term use and greater bone mass and density loss compared to non-users. This emphasizes the need for personalized risk assessment and careful dosage.

Protecting Your Bones While Taking Levothyroxine

Balancing effective thyroid treatment with bone protection is vital. Using the lowest effective dose to maintain a healthy TSH level is generally recommended. Regular monitoring is essential as thyroid needs can change.

Lifestyle Modifications for Bone Health

Supporting bone health through lifestyle changes is important:

Ensure Adequate Calcium and Vitamin D Intake: These are crucial for strong bones. Discuss appropriate intake and potential supplementation with your doctor.
Engage in Weight-Bearing Exercise: Activities like walking and strength training help build bone density.
Quit Smoking and Limit Alcohol: Both negatively impact bone health.
Get Regular Bone Density Screenings: DEXA scans can help monitor BMD, especially for older adults on long-term levothyroxine.

The Effect of Levothyroxine on Bone: A Comparison

Here is a comparison of outcomes based on treatment approach:


Feature	Euthyroid (Controlled) Levothyroxine Therapy	Overtreatment/TSH Suppression Therapy
Effect on Bone	Generally safe; studies show minimal to no significant adverse effect on bone mineral density (BMD).	Increased bone turnover, leading to decreased BMD and increased osteoporosis risk, especially in postmenopausal and older adults.
Associated Risk	Low risk of fractures, similar to the general population when well-controlled.	Higher risk of bone fractures, with some studies showing a dose-dependent increase in fracture risk.
Patient Profile	Individuals with hypothyroidism (subclinical or overt) maintained at an optimal, physiological dose.	Patients needing TSH suppression for conditions like thyroid cancer, or individuals who are inadvertently over-replaced.
Monitoring	Regular TSH monitoring is necessary to ensure the dosage remains appropriate.	Very close monitoring of both thyroid hormones and bone health (e.g., DEXA scans) is essential.

Conclusion: Navigating Treatment with Awareness

Does levothyroxine affect your bones is a question with a nuanced answer depending on dosage, age, and health. While vital for hypothyroidism treatment, it carries potential risks, particularly with long-term overtreatment or TSH suppression. For most on a stable, appropriate dose, the risk is low. However, recent research suggests bone density should be considered for all patients, especially older adults. Regular dialogue with your doctor, thyroid function tests, and bone health strategies are key to minimizing potential adverse effects and ensuring both thyroid function and bone integrity are maintained.

For more information on bone health, consult resources from the National Institutes of Health.

Frequently Asked Questions

Yes, but it is typically associated with receiving too high a dose for a prolonged period, which leads to over-replacement of thyroid hormone. When the dosage is properly controlled, the risk of developing osteoporosis is low.

Yes, studies have shown a link between higher levothyroxine dosages and increased risk of bone density loss, particularly in elderly women. Maintaining the lowest effective dose is recommended to mitigate this risk.

Yes, older adults and especially postmenopausal women are more susceptible to the bone-related side effects of levothyroxine. A 2024 study specifically noted an association with greater bone loss in older adults on the medication.

You can protect your bones by working closely with your doctor to ensure your dose is not excessive, getting regular bone density screenings, and adopting bone-healthy lifestyle habits, including adequate calcium and vitamin D intake, and weight-bearing exercise.

Regular therapy aims for normal TSH levels, posing minimal bone risk when well-managed. TSH suppression therapy, which uses intentionally high doses to treat conditions like thyroid cancer, carries a higher risk of accelerated bone loss.

After starting or adjusting levothyroxine, blood tests to check TSH are typically done every 6-8 weeks until stable. Once stable, monitoring is usually required once or twice a year to ensure the dose remains appropriate.

Yes. Patients with overt hypothyroidism, whose bone metabolism was slowed, may see an initial increase in turnover upon starting levothyroxine. In contrast, patients with subclinical hypothyroidism may have no significant adverse bone effect from low-dose therapy, provided TSH levels stay normal.