Levothyroxine, a synthetic version of thyroxine, is widely recognized as the gold standard in treating hypothyroidism. However, a recent study highlights a potential concern regarding its use among older adults. Conducted among individuals aged 65 or older, the study suggests that prolonged daily use of levothyroxine may be associated with increased bone loss, even when thyroid levels remain within the normal range. This revelation calls for a closer examination of how levothyroxine is prescribed and monitored, especially since it is the second most commonly prescribed drug among older adults in the United States.
The study involved 81 participants who were regular users of levothyroxine and 364 non-users. All participants had at least two doctor visits during which blood work confirmed normal levels of Thyroid Stimulating Hormone (TSH) and free T4. Despite maintaining these accepted normal ranges, those taking levothyroxine daily over six years exhibited greater bone loss compared to non-users. This finding raises concerns about the long-term effects of the medication on bone health in older adults.
Dr. Shadpour Demehri, one of the study's authors, noted:
“Levothyroxine use appears to be associated with greater bone loss in older adults.”
Levothyroxine, which is marketed under various brand names including Synthroid, is used by approximately 23 million Americans daily. The medication's usage is so prevalent that it accounts for 7% of the nation's population relying on it for managing hypothyroidism. Given this widespread use, understanding its full implications on health, particularly bone density, is crucial.
The potential link between levothyroxine and bone loss emerges from the hormone's role in the body. Levothyroxine can lead to an excess of thyroid hormone when not appropriately dosed, which in turn might contribute to bone degradation. Dr. Elena Ghotbi explained:
“When thyroid medication is given in excess, then people have more thyroid hormone than they need.”
However, Dr. Aaron Schulman emphasized that many patients absolutely require levothyroxine for their well-being:
“Many patients absolutely need to take levothyroxine.”
He also acknowledged that while levothyroxine remains the safest and most widely used option to treat an underactive thyroid, careful management of dosages is essential to mitigate potential side effects such as bone loss:
“Levothyroxine remains the safest and most widely used option to treat underactive thyroid.”
The study's findings do not suggest an immediate need to halt levothyroxine use among all older adults but rather underscore the importance of tailored dosing. Dr. Schulman elaborated on this point:
“If that is the case, the answer may not necessarily be stopping the levothyroxine, but rather, adjusting the dose to maintain thyroid hormone levels targeting a specific part of the normal reference range.”
Despite these findings, there is no strong evidence that levothyroxine use causes bone loss among euthyroid patients—those whose thyroid function tests are normal without medication. Moreover, doctors express less concern about bone loss in premenopausal women who take levothyroxine while maintaining normal thyroid hormone levels.
The study's robust design has been acknowledged by experts like Dr. Schulman, who affirms its contribution to understanding levothyroxine's broader impacts:
“The study was well-designed.”
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