Widely used thyroid pill may be linked to bone loss

A widely used pill for treating an underactive thyroid may be associated with bone loss, according to a study being presented next week at the annual meeting of the Radiological Society of North America in Chicago.

The drug, levothyroxine, is a synthetic version of the hormone produced by the thyroid gland. About 23 million Americans, some 7% of the U.S. population, take generic levothyroxine or the branded version sold by AbbVie ABBV.N as Synthroid, daily.

In a study of nearly 450 older adults, including 81 taking levothyroxine, the drug was associated with greater loss of total body bone mass and bone density over a median follow-up of 6.3 years.

This was true even though users' thyroid hormone levels were in the normal range.

“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 of Johns Hopkins University School of Medicine in Baltimore, who worked on the study, said in a statement.

Co-author Dr. Jennifer Mammen, also of Johns Hopkins, advises that adults taking levothyroxine should discuss their treatment with their healthcare provider.

“A risk-benefit assessment should be conducted, weighing the strength of the indications for treatment against the potential adverse effects,” she said.