Commonly Prescribed Medication for Older Adults Linked to Bone Loss, Study Finds

A worker is seen at a Florida pharmacy, in a file photo. Joe Raedle/Getty Images

One of the most-prescribed drugs in the United States for older adults has been linked to bone loss in a new study, officials said on Nov. 25.

Researchers with the Johns Hopkins University School of Medicine found in a study that levothyroxine, a synthetic hormone often used to treat hypothyroidism, may be associated with bone loss, a disease that weakens bones and causes them to be more likely to break. Common brand names for levothyroxine include Synthroid, Unithroid, and Tirosint.

About 23 million Americans, or about 7 percent of the entire U.S. population, take the medication on a daily basis, according to a statement issued by the Radiological Society of North America (RSNA), which announced the findings of the study that will be presented at the society’s annual meeting in December.

It’s the second-most prescribed medication for older adults in the country, according to the statement. An article from the Yale School of Medicine in 2023 called levothyroxine “one of the most prescribed drugs in the country.”

The Johns Hopkins authors linked the usage of levothyroxine to a higher degree of loss in bone density and bone mass over a more than six-year period, even in adults who have normal thyroid function.

The researchers used the Baltimore Longitudinal Study of Aging cohort study of older adults. People ages 65 and older who had at least two thyroid-function test visits were included in the data cited by the study, according to the statement.

The group that was observed in the study included 81 euthyroid levothyroxine users and 364 nonusers, with a median age of 73. Other risk factors such as age, gender, height, weight, race, other medications, and history of alcohol use and smoking were also factored into the research that matched levothyroxine users against non-levothyroxine users.

They also had median thyroid-stimulating hormone levels (TSH) of 2.35 during their initial visit, according to the study authors.

“Levothyroxine use was associated with greater loss of total body bone mass and bone density—even in participants whose TSH levels were within the normal range—over a median follow-up of 6.3 years,” the authors wrote. “This remained true when taking into account baseline TSH and other risk factors.”

“Our study suggests that even when following current guidelines, levothyroxine use appears to be associated with greater bone loss in older adults,” Dr. Shadpour Demehri, the study’s co-author and professor of radiology at Johns Hopkins, said in the statement.

The lead author of the study, Elena Ghotbi of Johns Hopkins, noted that their data also show that “a significant proportion of thyroid hormone prescriptions may be given to older adults without hypothyroidism, raising concerns about subsequent relative excess of thyroid hormone even when treatment is targeted to reference range goals.”

The maker of Synthroid also said on its website that taking too much levothyroxine can lead to a higher degree of bone loss, especially in women who are post-menopausal.

AbbVie, the maker of the brand, stated that “taking too much or too little” of the medication may lead to “negative effects on growth and development, heart function, bone health, reproductive function, mental health, digestive function, and changes in blood sugar, and cholesterol metabolism in adult or pediatric patients.”