Warning after one of the most prescribed drugs in Britain is linked to debilitating bone diseases

Thousands of Britons taking medication for a common hormone condition may be at risk of bone loss, research suggested today.

About one in five Britons suffer from an underactive thyroid, caused by problems with the butterfly-shaped gland in the neck that controls functions from digestion to heart rate and mood.

Still, levothyroxine, pills that cost just a few cents a day to combat the condition, could increase the risk of the bone-thinning disease osteoporosis.

Research has long suggested that too much thyroid hormone accelerates bone loss, increasing the risk of the disease.

But now the US scientists who assessed the drug in dozens of patients found that this risk is still increased in those with ‘normal’ levels of the thyroid-stimulating hormone.

Professor Shadpour Demehri, an expert in radiology at John Hopkins University in Maryland and co-author of the study, said: ‘Our study suggests that even when current guidelines are followed, the use of levothyroxine appears to be associated with greater bone loss in older adults.”

Dr. Elena Ghotbi, lead author of the study and postdoctoral researcher at John Hopkins University added: ‘Data indicate that a significant proportion of thyroid hormone prescriptions could be given to older adults without hypothyroidism.

‘This raises concerns about subsequent thyroid hormone excess, even if treatment is aimed at reference targets.’

About one in five Britons suffer from an underactive thyroid, caused by problems with the butterfly-shaped gland in the neck that regulates functions from digestion to heart rate and mood.

Levothyroxine, sold under the brand name Eltroxin, is one of the most commonly prescribed drugs in Britain.

About 1.36 million people in England use it and the number of prescriptions increased by 9 percent between 2016 and 2022, according to figures published in The Lancet last year.

In the study, researchers assessed 81 patients who used levothyroxine and 364 non-users, with an average age of 73 years and a thyroid-stimulating hormone level of 2.35.

Normal levels are typically 0.4 to 4.0 milliunits per liter (mU/L).

Over a six-year follow-up, they found that those taking levothyroxine suffered “greater loss of total body bone mass and bone density.”

Patients taking the drug who had “normal” thyroid-stimulating hormone levels also suffered loss of bone mass and density, the researchers added.

Dr. Jennifer Mammen, co-author of the study and associate professor of endocrinology at Johns Hopkins, said adults taking levothyroxine should discuss their treatment with a doctor and regularly monitor their thyroid function tests.

She said: ‘A risk-benefit analysis should be carried out, weighing the strength of the indications for treatment against the potential adverse effects of levothyroxine in this population.’

Research has long suggested that too much thyroid hormone accelerates bone loss, increasing the risk of the bone-thinning disease osteoporosis. Pictured: An X-ray of the head of a femur of the femur affected by osteoporosis

The research will be presented in full next week in Chicago at the annual meeting of the Radiological Society of North America.

According to the British Thyroid Foundation, an underactive thyroid is not a risk factor for osteoporosis.

However, adults prescribed levothyroxine should have regular blood tests, at least once a year, to ensure thyroid hormone levels are ‘not too high’, they advise.

‘Continuously high thyroid hormone levels can lead to the development or worsening of low bone density and osteoporosis.’

Figures show that at least one in twenty people in Britain have a thyroid condition.

The thyroid gland produces two important hormones – triiodothyronine (T3) and thyroxine (T4) – that help regulate important body functions, including heart rate, temperature and mood.

Hypothyroidism, in which the gland produces too few hormones, leading to weight gain, fatigue, feeling cold, constipation and dry skin and hair.

Women are ten times more likely to be affected than men, although it’s not clear why – and the most common cause of both thyroid problems is an autoimmune disease, where the body mistakenly attacks the thyroid tissues.

There are 3.5 million people in Britain with osteoporosis, but it is often known as a ‘silent disease’ because there are no symptoms until someone breaks a bone.

Half of all women and one in five men over 50 will suffer a fracture, usually in the spine or hips, because of the disease, which makes bones so fragile that a break can be caused by coughing or sneezing.

Such fractures are the fourth biggest cause of disability and premature death in Britain.