One of the most common prescription drugs might be putting you at a higher risk for losing bone density, according to new research.
Roughly 23million Americans take levothyroxine, also known by the brand name Synthroid, every day, making it the second most commonly used drug in older adults in America.
It’s prescribed to people who have problems with their thyroid, a butterfly shaped gland in the neck that controls energy, weight and hair growth. Hypothyroidism affects about one in 20 Americans over age 12.
Older research has found that having too much thyroid hormone in the body raises someone’s risk for bone fracture. Knowing this, researchers from Johns Hopkins investigated the effect that taking levothyroxine had on bone health.
By studying dozens of people over six years, they found people who were taking the drug were more likely to lose a larger amount of bone tissue than people who were not taking the drug.
Professor Shadpour Demehri, an expert in radiology at John Hopkins University in Maryland and study co-author said: ‘Our study suggests that even when following current guidelines, levothyroxine use appears to be associated with greater bone loss in older adults.’
Low bone density can lead someone to become more frail and prone to bone fractures – in a condition known as osteoporosis.
Levothyroxine, pills that cost just a few pence a day to combat the condition, could raise the risk of losing bone mass and bone density
The thyroid is a gland in the neck that releases chemicals that control metabolism and energy
In the study, researchers assessed 81 patients on levothyroxine and 364 non-users, with an average age of 73 and thyroid-stimulating hormone level of 2.35.
The research will be presented in full at the Radiological Society of North America’s annual meeting next week in Chicago.
Normal levels are typically 0.4 to 4.0 milliunits per liter (mU/L).
Over a follow-up of six years, they found those on levothyroxine suffered a ‘greater loss of total body bone mass and bone density’.
Patients taking the drug who had a ‘normal’ thyroid-stimulating hormone level also suffered bone mass and density loss, the researchers added.
Dr Jennifer Mammen, study co-author and associate professor of endocrinology at Johns Hopkins, said adults taking levothyroxine should discuss their treatment with a medic and regularly monitor their thyroid function tests.
She said: ‘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.’
This could also suggest that Synthroid is being over prescribed, Dr Elena Ghotbi, study lead author and postdoctoral research fellow at John Hopkins University said.
Dr Ghotbi said: ‘Data indicates that a significant proportion of thyroid hormone prescriptions may be given to older adults without hypothyroidism.
This isn’t the first paper to take a critical look at the drug. According to 2023 research from Yale School of Medicine, about 90 percent of people who take the drug may not need it.
Dr Joe El-Khoury, a professor of laboratory medicine, who led the research said: ‘Study after study has shown that there is greater risk when you overtreat with levothyroxine in patients who may not need it.’
The Johns Hopkins researchers didn’t study osteoporosis specifically, but low bone density is precursor to this condition, which affects roughly 10million people over age 50.
This X-ray shows a female with a broken hip, which is one of the most debilitating breaks associated with osteoporosis, according to Yale. Thyroid problems are much more common in women than in men.
In osteoporosis, holes inside the bone widen and cause the outer walls of the bone to thin, becoming brittle and easily breakable.
Then, one someone has a small tumble, they can be at risk for major bone breaks – including hip fractures.
According to Yale School of Medicine, these hip fractures can cause someone to lose mobility, independence and have been linked to an earlier death.
Osteoporosis becomes much more common with age – but the odds of developing the condition increase if someone smokes, has a poor diet, has arthritis or bone cancer.
In addition, hormones play a role in bone health. This includes thyroid hormones, sex hormones like estrogen and testosterone and growth hormones like insulin.
Women are five to eight times more likely to develop thyroid problems than men.
It’s unclear what causes these disorders, but if they go untreated, they can cause heart disease and infertility, according to American Thyroid Association.
Researchers are unsure why thyroid hormones can cause these changes to bone. In a healthy body, scientists from the Imperial College London have shown that these hormones help control the rate that new bone replaces cartilage, the dense spongy centers of bone.
This helps maintain bone health, which includes regulating the rate that bone tissue is lost.
So, the theory is that if there is too much thyroid hormone in the body, the rate that bone tissue is lost outpaces the rate of new bone added, leading to osteoporosis.
Still, research is divided, and the Johns Hopkins team said more studies are needed to prove there is a link between the two.
