Weight loss drugs raise thyroid cancer risk

When it comes to weight loss pills, the new kids on the block have been heralded as a silver bullet when it comes to tackling obesity-related illnesses. But are there also drugs contained within them that should give us cause for concern? Anne McTiernan is an epidemiologist and obesity researcher at the Fred Hutchinson Cancer Center in Seattle. She studies ways to prevent new or recurrent cancer through lifestyle factors such as weight control, and began by explaining how drugs like Ozempic work…

Anne - They've been very well tested for people with diabetes as a secondary medication for those patients. And they've also now been tested for weight loss and they've been shown to produce significant amounts of weight loss if they can tolerate them. Also reduces the risk of several diseases like heart disease. And these have been tested in clinical trials. Those are the gold standards of research, when you're looking at the effects of a medication.

Chris - There are a host of diseases, cancers specifically, that are actually linked to obesity, things like breast cancer. So presumably one can expect that if you use these agents and you shed weight, in fact you are reducing your risk of those cancers, which are linked to obesity.

Anne - There are about 13 cancers that are increased in risk in people with high levels of body weight. The problem is we don't know if people lose weight, if that will reverse that relationship. The gold standard for testing would be clinical trials, but these clinical trials would take many, many years and many people to show an effect.

Chris - Nevertheless, there have been some claims of an increase in certain types of cancers in people who are using these agents. That's true, isn't it?

Anne - Yes. And there was what we call a systematic review and meta-analysis of the clinical trials that have been done in these medications. And there is a suggestion of increased risk of thyroid cancer. There wasn't any evidence of increased death from cancer, but there was evidence of increased thyroid cancer. So this is something for patients to know who are taking these medicines for some reason, that it's a good idea to keep getting thyroid checks.

Chris - When epidemiologists are thinking about possible links between one thing causing another, the thing that they're drawing that connection between, it has to be biologically plausible. So have doctors and scientists come up with a way to link taking these drugs with this outcome of thyroid cancer?

Anne - To my knowledge, there has been some amount of work in that area. For this reason some doctors will say people that have a particular genetic risk for thyroid cancer that it might not be a good medication for them. But reducing weight, we have some evidence from observational studies that surgical treatment of obesity can reduce cancer risk, some evidence from dietary weight loss, but we don't yet have evidence for these new types of weight loss medication.

Chris - Is it not a concern though, that these agents are effectively available to people who want to take them and people can access them relatively easily? So we, we may have a link to these agents causing a particular form of cancer and people nevertheless can access them and use them

Anne - In the United States they are extremely expensive. So they're not available to the vast majority of people unless they have diabetes and they have very good insurance. And when we're talking about potential risk of thyroid cancer, it's an extremely small risk. So yes, patients need to know about recent benefits of any medication, but for most people their risk of thyroid cancer would be extremely small. But the benefit of reducing weight, especially if somebody has diabetes, is going to be significant.