Levothyroxine, a widely used medication for treating hypothyroidism, may be linked to bone loss, according to a recent study. The drug, sold under brand names such as Synthroid, is the second most frequently prescribed medication among older adults in the United States, with approximately 7% of the population consuming it. Hypothyroidism, a condition characterized by an underactive thyroid, affects an estimated 30 million Americans and is often associated with symptoms such as fatigue, weight gain, and hair loss.
The study, conducted by researchers from Johns Hopkins Medicine, found a correlation between the use of levothyroxine and a significant loss of bone mass and bone density over a six-year period. This was observed even in older adults with normal thyroid function. The preliminary research involved a comparison of the bone health of 81 levothyroxine users and 364 non-users, most of whom were in their early 70s.
Dr. Shadpour Demehri, co-senior study author and professor of radiology at Johns Hopkins, stated, “Our study suggests that even when following current guidelines, levothyroxine use appears to be associated with greater bone loss in older adults.” The manufacturers of Synthroid have acknowledged that excessive consumption of levothyroxine can lead to increased bone loss, particularly in post-menopausal women.
The loss of bone mineral density and bone mass is a condition known as osteoporosis, which affects an estimated 10 million Americans aged 50 and above. Osteoporosis weakens the bones, making them more prone to fractures. It can also make movement difficult and recovery from broken bones challenging. In severe cases, fractures can lead to life-threatening complications.
The study authors expressed uncertainty as to why some patients were initially prescribed levothyroxine and why they continue to take it. Dr. Elena Ghotbi, the study’s lead author and a postdoctoral research fellow at Johns Hopkins, noted, “Data indicates 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 findings of the study will be presented at the upcoming annual meeting of the Radiological Society of North America. In the meantime, adults taking levothyroxine are advised to consult their doctors to weigh the benefits of the treatment against potential bone loss and other possible adverse effects.