What it means
In studies in rodents, semaglutide, tirzepatide, liraglutide and dulaglutide caused thyroid C-cell tumors. It is not known whether these drugs cause such tumors, including MTC, in people.
Because of that uncertainty, the labels carry a boxed warning and say not to use these medicines in people with a personal or family history of MTC or with MEN 2.
The labels tell patients to report symptoms such as a lump or swelling in the neck, trouble swallowing, hoarseness or shortness of breath.
Routine thyroid ultrasounds or calcitonin blood tests are not required by the labels for everyone starting these drugs. Your prescriber decides whether any testing makes sense for you. MTC is rare, making up a small share of all thyroid cancers. Some cases run in families, often tied to MEN 2.
Why it matters
A family history of MTC is one of the few absolute reasons not to take these medicines.
Related terms
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