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Thyroid Drug: A Silent Threat to Bone Health

• Levothyroxine, a common thyroid medication, is linked to bone loss in older adults.
• The study found that even with normal thyroid function, levothyroxine use was associated with greater loss of total body bone mass.
• The findings highlight the risks of long-term use of levothyroxine, emphasizing the need for regular monitoring and reevaluation.
• The study serves as a reminder of the delicate balance between the benefits and potential risks of long-term medication use.

A groundbreaking study has raised concerns about levothyroxine, a synthetic version of the hormone thyroxine, commonly prescribed to patients with underactive thyroid. The study links the use of this medication to bone loss, particularly in older adults. This revelation is significant as levothyroxine is the second most commonly prescribed thyroid medication for older adults in the U.S.

Underactive thyroid or hypothyroidism is characterized by symptoms such as fatigue, increased heart rate, depression, dry skin and hair, muscle cramps, constipation, weight gain, and memory issues. Approximately 23 million U.S. adults take levothyroxine, sold under brand names Synthroid, Levoxyl, Unithyroid, and Tirosint. However, the study noted that many patients continue the medication for years without checking if it's still required or fully understanding the reasons for its initial prescription.

Dr. Elena Ghotbi, the study's lead author and postdoctoral research fellow at Johns Hopkins University School of Medicine, expressed concerns about the significant proportion of thyroid hormone prescriptions given to older adults without hypothyroidism. This raises concerns about the subsequent relative excess of thyroid hormone even when treatment is targeted to reference range goals.

The Impact of Levothyroxine on Bone Health

The study investigated the link between levothyroxine use in older euthyroid adults (those with normal thyroid function) and increased bone loss over time. The researchers evaluated bone loss over time in 81 euthyroid levothyroxine users and compared it against 364 non-users with similar risk factors. They found that even in participants whose TSH levels were within the normal range, levothyroxine use was associated with greater loss of total body bone mass and bone density after a follow-up of around 6.3 years.

Dr. Shadpour Demehri, co-senior author and professor of radiology at Johns Hopkins, stated that even when following current guidelines, levothyroxine use appears to be associated with greater bone loss in older adults. This finding was presented at the Radiological Society of North America (RSNA) 2024 meeting.

The study's findings are significant as they highlight the potential risks associated with long-term use of levothyroxine, particularly in older adults. It underscores the importance of regular monitoring and reevaluation of the need for continued medication in patients with underactive thyroid. It also emphasizes the need for healthcare providers to educate patients about the potential risks and benefits of long-term levothyroxine use.

Historical Similar Events and Conclusion

In the past, similar concerns have been raised about the long-term use of other commonly prescribed medications. For instance, studies have shown that long-term use of proton pump inhibitors, commonly prescribed for acid reflux, can lead to bone loss and increased risk of fractures. Similarly, long-term use of corticosteroids, used to treat conditions like asthma and arthritis, has been linked to osteoporosis and increased fracture risk.

The findings of this study add to the growing body of evidence highlighting the potential risks associated with long-term use of commonly prescribed medications. It underscores the importance of regular monitoring and reevaluation of the need for continued medication in patients with chronic conditions. It also emphasizes the need for healthcare providers to educate patients about the potential risks and benefits of long-term medication use.