Study Finds Link Between Bone Fractures and Thyroid Medications

Some thyroid medications may raise the risk of bone fractures among the elderly, according to the findings of a recent study. 

Research published last week by the British Medical Journal indicates that side effects of Levoxyl and Synthroid nearly doubled the risk of bone fractures for individuals 70 years or older. Fractures on the thyroid medications were found to be more common with medium to high doses and among women.

Canadian researchers looked at more than 213,000 people age 70 or older who took the thyroid drugs over a nearly four-year-period. They found that more than 22,000 suffered a bone fracture during that time, about 18,000 of which were women. They determined users had a 88% increased risk of bone fracture over people who did not take the drug. Women in particular had a higher risk of hip fractures.

The data appear to indicate that the Levoxyl and Synthroid fracture risk is dose-specific. Users who took medium doses of between 0.044 and 0.093 mg/day and those who took high doses of above 0.093 mg/day were at a higher risk of bone fractures than those who took low doses, researchers found.

Levoxyl and Synthroid (levothyroxine) is a synthetic thyroid hormone that is used to treat hypothyroidism. It was approved by the FDA in 2001 and is available in a number of other brand names as well, including Levo-T, Levolet, Levothroid, Novothyrox, Tirosint and Unithroid.

The researchers said that it appears that the drugs are associated with a significant increase in the risk of bone fractures that has a strong dose-response relation. The researchers pointed out that health care providers should monitor the drugs’ uses carefully to prevent overtreatment. The scientists said that elderly patients needed smaller doses as they got older. They said that the average daily dose among users turned out to be between 0.076 and 0.122 mg/day.