Levothyroxine – a common medication taken for hypothyroidism – may be associated over time with bone loss, according to a study to be presented at next week’s RSNA meeting in Chicago.
Researchers from Johns Hopkins University in Baltimore, MD, will share findings that suggest that people taking the medication over about six years had greater loss of total body bone mass and bone density compared with nonusers. What’s more, the bone loss was seen even in participants whose thyroid-stimulating hormone (TSH) levels were within normal range, noted co-senior author Shadpour Demehri, MD.
“Our study suggests that even when following current guidelines, levothyroxine use appears to be associated with greater bone loss in older adults,” Demehri said, in a news release from RSNA.
Approximately 23 million Americans -- about 7% of the U.S. population -- take levothyroxine daily, most commonly for hypothyroidism, a condition in which the thyroid glands do not produce enough thyroxine. If left untreated, the condition can lead to serious and potentially fatal complications.
Levothyroxine pills. Image courtesy of RSNA.
However, some patients have been taking levothyroxine for many years, even though it is not clear why it was initially prescribed, or even if it is still required, the researchers explained. Moreover, an excess of thyroid hormone is associated with increased risk of bone fracture, they noted.
Thus, the group aimed to determine whether levothyroxine use is associated with bone loss over time in older “euthyroid” adults, meaning adults with normal thyroid function. Though there are some variables, a normal reference range for TSH is typically around 0.4 to 5 microunits per ml.
The researchers analyzed data from 81 euthyroid levothyroxine users (32 men, 49 women) and 364 matched nonusers (148 men, 216 women), with a median age of 73 and TSH levels of 2.35 at the initial visit. Participants had at least two visits and thyroid function tests consistently within the reference ranges at each visit, as well as dual-energy x-ray absorptiometry scans to measure bone density and mass.
According to the results, over a median follow-up of 6.3 years, levothyroxine use was found to be associated with greater longitudinal loss of total body bone mass (beta coefficient: -6.53, p < 0.001) and total body bone density (beta coefficient: -0.0014, p < 0.001).
Co-senior author Jennifer Mammen, MD, PhD, added that adults taking levothyroxine should discuss their treatment with their healthcare 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.
