A recent study presented at the Radiological Society of North America (RSNA) annual meeting indicates that levothyroxine, a common medication for hypothyroidism, may be associated with bone loss in older adults, even when thyroid function is within the normal range. The research raises concerns about the long-term effects of levothyroxine on bone health in this population.
Study Details and Findings
The study, a collaboration between Johns Hopkins Medical Institutions and the Baltimore Longitudinal Study of Aging (BLSA), included 81 euthyroid levothyroxine users (32 men, 49 women) and 364 non-users (148 men, 216 women), with a median age of 73 and TSH levels of 2.35 at the initial visit. Researchers analyzed data from the BLSA, a long-term observational study, to assess changes in bone density over time.
After a median follow-up of 6.3 years, the results showed that levothyroxine use was associated with a greater loss of total body bone mass and bone density, even in participants whose TSH levels were within the normal range. This association remained significant after accounting for baseline TSH levels and other risk factors such as age, gender, height, weight, race, medications, smoking history, and alcohol use.
Expert Commentary
"Our study suggests that even when following current guidelines, levothyroxine use appears to be associated with greater bone loss in older adults," said Shadpour Demehri, M.D., co-senior author and professor of radiology at Johns Hopkins.
Jennifer Mammen, M.D., Ph.D., co-senior author and associate professor of endocrinology at Johns Hopkins, advises that adults taking levothyroxine should discuss their treatment with their health care provider and regularly monitor their thyroid function tests. "A risk-benefit assessment should be conducted, weighing the strength of the indications for treatment against the potential adverse effects of levothyroxine in this population," she said.
Implications for Clinical Practice
The findings suggest that healthcare providers should carefully consider the potential risks and benefits of levothyroxine treatment in older adults, even when thyroid function appears normal. Regular monitoring of thyroid function and bone density may be warranted in patients taking levothyroxine to mitigate potential bone loss.
Background on Levothyroxine and Hypothyroidism
Levothyroxine, marketed under brand names like Synthroid, is a synthetic version of thyroxine, a hormone produced by the thyroid gland. It is commonly prescribed to treat hypothyroidism, a condition in which the thyroid gland does not produce enough thyroxine, leading to symptoms such as fatigue, weight gain, and hair loss. Approximately 23 million Americans, about 7% of the U.S. population, take levothyroxine daily.
Study Limitations
The study is observational and does not prove a causal relationship between levothyroxine use and bone loss. Further research is needed to confirm these findings and to determine the optimal management strategies for older adults taking levothyroxine.
