An obese man was left in excruciating pain and forced to go to emergency after a slimming injection caused his thyroid to become overactive.
The 62-year-old, who also had type 1 diabetes, lost more than 36kg in less than six months on tirzepatide, sold under the brand name Mounjaro.
But after being rushed to hospital with sudden palpitations, fever and even hand tremors, scans showed he had developed an irregular heart rhythm, atrial fibrillation, dubbed the “silent killer”.
Doctors also discovered she had thyrotoxicosis, a condition in which the thyroid gland, responsible for metabolism and heart rate, malfunctions, with potentially fatal consequences.
Sharing their case in a medical journal as a warning, the doctors today called for those using the slimming injections to be monitored more closely to prevent “adverse events.”
The 62-year-old, who also had type 1 diabetes, lost more than 36kg in less than six months taking tirzepatide, sold under the brand name Mounjaro. But after going to hospital with sudden palpitations, fever and even hand tremors, scans showed he had developed atrial fibrillation, known as the “silent killer”.
According to the latest data, the most common side effects of tirzepatide, the active ingredient in Mounjaro, were digestive problems. Among them, about one in five participants experienced nausea and diarrhea, and about one in ten reported having vomited or diarrhea.
U.S. health officials have already approved Mounjaro for weight loss, hailing it as a game-changer in the fight against obesity, which costs billions of dollars in health care costs.
It also became privately available in Britain in February, with clinics charging around £40 for a week’s supply.
Studies have found that the drug, made by US pharmaceutical giant Eli Lilly, could help obese people lose more than 20 per cent of their body weight in less than a year and a half.
But like all medicines, Mounjaro is not without side effects.
The European Medicines Agency said this year that research in rodents has suggested that artificial hormones contained in tirzepatide could increase the risk of medullary thyroid cancer.
In a paper published in the journal JAMA Internal Medicine, researchers at the University of Colorado said the unnamed male patient, who had a BMI of 31.2, presented to the emergency department with palpitations, excessive sweating, confusion, fever and hand tremors.
She had been prescribed tirzepatide six months earlier, initially at a weekly dose of 2.5 mg, and also took levothyroxine to help control her diabetes.
“The physician suggested increasing the dose of tirzepatide every four weeks as tolerated and following up at 1 month,” they noted.
However, the man did not attend his follow-up appointment, but nevertheless increased his dosage and was taking 10 mg weekly.
Doctors said the atrial fibrillation was caused by thyrotoxicosis following “rapid weight loss due to tirzepatide.”
They added: ‘We recommend closely evaluating patients using tirzepatide (initially every four to six weeks) for response to therapy, adverse events, and possible dose adjustment of other concomitant medications.
Tirzepatide is part of a class of drugs known as GLP-1 receptor agonists: these treatments trick the brain into thinking it is full, thereby reducing appetite.
However, the huge global demand has also caused counterfeit versions to flood the market.
Pharmacists warned yesterday of an “explosion” of fake weight-loss vaccines, fuelled by a shortage of Ozempic, which contains semaglutide.
Wegovy and Ozempic work by stimulating the body to produce a hormone called GLP-1 that is naturally released from the intestines after meals.
Health authorities have already seized more than 800 potentially counterfeit slimming pens across the UK since the start of 2023.
Counterfeit vaccines have been found in the past to contain insulin, a drug used by diabetics.
Insulin works by rapidly lowering blood sugar levels, but if sugar levels are not raised early on, doing so can have serious and potentially fatal consequences.
Semaglutide has been available on the NHS since 2019, and in the US since 2017, for type 2 diabetics. control blood sugar levels.
But its manufacturer Novo Nordisk is also investigating whether semaglutide (the active ingredient in the popular weight-loss vaccines Ozempic and Wegovy) could increase the risk of medullary thyroid cancer and pancreatic cancer.
However, there is still no evidence to show that these are definitely side effects, even in extremely rare cases.
All Britons are urged to report any medication side effects they notice to the MHRA Yellow Card Scheme.
British ministers are planning to distribute the drugs to millions of overweight Britons to combat the obesity crisis. In future, children could also be vaccinated.
The latest NHS data shows that 26 per cent of adults in England are obese and a further 38 per cent are overweight but not obese.
In the United States, it is estimated that 41.9 percent of the adult population is obese.