Janumet contains sitagliptin, a new anti-diabetes medication that has been linked to several cases of thyroid cancer. It is unknown if Janumet causes thyroid cancer, because thyroid cancer is very rare and Janumet is relatively new. Researchers are currently conducting long-term studies to investigate the risk of thyroid cancer.

Does Janumet Cause Thyroid Cancer?

Experts do not know if Janumet causes thyroid cancer. It is possible that Janumet can cause thyroid cancer, but difficult to study for the following reasons:

  • Thyroid cancer is very rare
  • Janumet has only been on the market since 2007
  • Patients who use Janumet often have other risk factors for developing thyroid cancer
  • Studies of cancer often take many years to complete

Between 2004 and 2009, two cases of thyroid cancer were reported in patients taking sitagliptin, according to a 2011 study published in Gastroenterology. After this study was published, the lead researcher cautioned:

“This analysis of the FDA database does not establish that pancreatitis, pancreatic cancer and thyroid cancer are caused by GLP-1 therapy. It simply raises the level of concern that they may be, and that the appropriate prospective studies are required to rule them out.”

How Could Janumet Cause Thyroid Cancer?

Janumet contains sitagliptin, one of two anti-diabetes drugs (the other is metformin). Sitagliptin treats diabetes by influencing GLP-1, a hormone that stimulates the pancreas to produce more insulin and lower blood-sugar levels. Another GLP-1 therapy drug, liraglutide, was shown to cause proliferation of cancerous thyroid C-cell tumors in rodents. The FDA published this Safety Communication about the risk in June 2011.

Due to the possibility that sitagliptin might also cause thyroid cancer, the U.S. Food and Drug Administration asked Amylin Pharmaceuticals to study this risk in 2009. However, that study will likely take many years to complete.

Causes of Thyroid Cancer

Thyroid cancer is caused when a cell in the thyroid gland starts growing and dividing out of control. No one knows exactly why this occurs, but possible risk factors include:

  • Diabetes drugs in the GLP-1 therapy class (such as Janumet)
  • High doses of radiation (especially in the neck region during childhood)
  • Family history of thyroid diseases
  • Individual history of goiters (enlarged thyroid tissues)
  • Asian ancestry
  • Being between 25-65 years old
  • Gender (75% of people who get thyroid cancer are female)
  • Other medical conditions, including:
    • Hashimoto’s thyroiditis
    • Cowden’s syndrome
    • Thyroid adenoma
    • Familial adenomatous polyposis
  • And more