How to weigh the benefits against the risks of popular weight-loss drugs
In the 1940s, cocktails of appetite suppressants — brightly colored capsules often containing amphetamines, diuretics, laxatives and thyroid hormones — were heavily marketed to American women to maximize weight loss.
Today, a bevy of new drugs have emerged as potentially safe “magic pills” to help people lose and manage weight. But while seemingly effective for shedding pounds — and addressing other health issues typically connected to obesity — the concern that weight-loss drugs like Ozempic, Rybelsus and Wegovy might be linked to thyroid cancer has been maybe they do, maybe they don't.
“All of these drugs are the same drug but in different formulations and given in different dosages. They’ve been on the market for a while, but they’ve gotten really hot for weight loss over the last couple of years,” explains Ryan McSpadden, MD, a Head & Neck / Plastic and Reconstructive surgeon at Roswell Park Comprehensive Cancer Center.
“Ozempic was originally approved for use in Type 2 diabetes. But longer-term studies following patients with Type 2 diabetes found that a significant portion of these patients were also losing weight, and that kind of spurred the interest of using it as a weight-loss drug.”
The new weight-loss prescriptions fall collectively under the generic identity of semaglutide. Rybelus is a pill taken daily and Ozempic is administered weekly by injection. Both are approved by the U.S. Food and Drug Administration (FDA) for treating Type 2 diabetes. Wegovy, also a weekly injectable, is FDA-approved specifically for weight loss.
How these weight-loss drugs work
All three drugs have the same active ingredient — semaglutide, a class of medications called glucagon-like peptide-1(GLP-1) agonists. Essentially, they make people feel full faster and longer.
“They work on the same receptor to stimulate it. By stimulating this receptor with these drugs, it helps with Type 2 diabetes by increasing insulin secretion and decreasing the amount of glucagon in the body, which helps to stimulate sugar release from the liver,” Dr. McSpadden says.
“The secondary benefit to semaglutide for weight loss is that it increases the amount of time it takes for food to pass from the stomach to the intestines. That makes you feel full sooner and longer, and then that decreases your appetite.”
FDA boxed warning for semaglutide
For many struggling with obesity, decreased appetite can be a great thing. But the FDA has issued a boxed warning (formerly “black box warning”) for Ozempic and Wegovy, citing a risk of thyroid tumors and cancer.
Specifically, the warning advises patients with a personal or family history of medullary thyroid cancer (MTC), or multiple endocrine neoplasia syndrome type 2 (MEN2) to avoid semaglutide medications.
“In earlier laboratory studies, researchers noticed an increased incidence of a specific type of thyroid cancer called medullary thyroid cancer. Medullary thyroid cancer is a rarer form of thyroid cancer that comes from a specific cell within the thyroid called parafollicular C cells that release calcitonin into the body, which is important for calcium regulation,” Dr. McSpadden says.
“Because of this, the FDA put a black box warning on all these types of medications to not use it for patients with a history or family history of medullary thyroid cancer. Medullary thyroid cancer makes up a small percentage of our total thyroid cancer patients, maybe about 3 to 10%.”
While researchers have found no incidence to date of semaglutide causing any kind of thyroid cancer in humans, the earliest laboratory research identifying a correlation between semaglutide and medullary thyroid cancers was strong enough for the FDA to warrant a boxed warning.
“Overall, the results have been mixed, with some trials saying that there’s no increased risk and some trials saying that there’s a slight increased risk. But there has been really no evidence to show that there is a substantial risk of non-medullary thyroid cancer associated with these weight loss drugs,” Dr. McSpadden says.
Symptoms and risks of thyroid cancer
Research shows that some factors may put you at a higher-than-average risk of developing the disease.
However, the FDA boxed warning is for Rybelsus as well as Ozempic and Wegovy. Other possible side effects of semaglutide listed by Novo Nordisk, which manufactures all three of the drugs, include:
- Pancreatitis
- Hypoglycemia
- Gall bladder issues
- Vision changes
- Increased heart rate
- Depression / suicidal thoughts
In July, the FDA issued a new boxed warning for these popular weight loss drugs in response to reports of people overdosing and taking as much as 20 times more than the intended dose. The FDA also warns about the potential of developing ileus, a blockage that keeps food or liquid from passing through the colon.
“If you are taking thyroid medications, the most common being Synthroid, it can affect medication levels,” Dr. McSpadden advises. “Because the effect of semaglutide on the stomach and the intestines causes a decrease in gastric emptying, the transit time of these medicines might increase, meaning that you can have increased absorption of them. Your levels of thyroid medicine may have to be adjusted.”
Risks vs. benefits of taking a weight-loss drug
If you are managing Type 2 diabetes, and struggling to lose weight, the benefit of taking expensive drugs like Ozempic, Rybelsus and Wegovy may outweigh the potential risks.
“Having better blood glucose control is beneficial to multiple areas of the body, including kidneys and cardiovascular risks. The weight loss is going to help improve blood pressure and decrease sleep apnea, so you have the potential to significantly improve with these drugs,” says Dr. McSpadden.
People who are already on thyroid medications will need more frequent monitoring of their thyroid levels and possible adjustments of medications because of absorption changes in the stomach and weight loss. If you do not have a thyroid issue, no additional monitoring besides routine thyroid checks by your doctor is recommended. Your physician should also feel your thyroid during routine physicals and order thyroid function labs with other routine labs as needed.
“If you have Type 2 diabetes and you’re obese, the benefit of better blood sugar control and weight loss is going to have a much more substantial benefit on your overall health than the annoyances of having to adjust and monitor thyroid medications, or the potentially small increased risk of thyroid cancer,” Dr. McSpadden adds. “I think it just goes to patients educating themselves on these medications and the potential side effects, and ranking the benefits of them versus potential risks.
For thyroid cancers and thyroid conditions, he advises coming to Roswell Park for diagnosis and treatment: “We have a high volume for performing thyroid surgeries, and a high-volume center will have the best outcomes with the least amount of complications, which has been proven time and again.”
