Elderly people being treated for hypothyroidism may have an excess risk of fragility fractures if their hormone levels are not regularly monitored and their levothyroxine dose adjusted for age, warn experts.
An editorial and research, published Online First today in the BMJ, caution that many elderly people have been on the same dose of levothyroxine since their hypothyroidism was diagnosed decades before, even though people’s requirement usually drops as they age. And a Canadian case-control study confirmed that “excessive” and even “medium” dosing increases patients’ risk of having a fracture.
Researchers in Toronto, Canada, designed their case-control study to test earlier reports of an association between levothyroxine and fractures, and quantify the effect of the drug on risk.
They compared fracture risk in people aged at least 70 years who were currently using levothyroxine, had recently used the drug, or had used it >180 days previously.
Men and women who were currently using or had recently used levothyroxine had a significantly higher risk of fractures than those who had not used the drug recently.
Even after allowing for other risk factors, there was a dose-response association between levothyroxine and fracture risk – hip and other fractures were significantly more likely with high and medium doses of levothyroxine than with low doses.
The authors conclude: “Our findings provide evidence that levothyroxine treatment may increase the risk of fragility fractures in older people even at conventional dosages, suggesting that closer monitoring and modification of treatment targets may be warranted in this vulnerable population.”
Professor Graham Leese from Ninewells Hospital in Dundee warns in his editorial that levothyroxine requirements may fall considerably as people age, and says elderly patients are often not monitored as they should be.
He says: “It is 120 years since the effect of excess thyroid hormone on bone was first described, yet research in this area still lacks funding. With the prevalence of treated hypothyroidism increasing, and the annual economic burden of fractures in the United Kingdom currently estimated at €5.8bn (£5.1bn; $8.4bn), such research warrants a higher priority.”