Metformin and Testosterone May Reduce Cancer Risk

Colorectal cancers remain the third most common cancer and third most common cause of cancer-related mortality in US men and women.In addition, rates of colon cancer in younger persons have been increasing. The incidence and mortality from colon cancer have been on a slow decline over the past several decades in the United States, with the incidence falling on average 2.4% each year and death rates falling on average 2.2% each year over 2007-2016. 

Prostate cancer represents the second most common cancer in men worldwide and the fifth most common cause of cancer death in men; in the United States, it is the most common cancer in men and the second most common cause of cancer deaths in men.

With an increasing prevalence of testosterone deficiency and diabetes in older men, metformin and testosterone replacement therapy are increasingly used in combination.

Metformin has been previously linked with a reduction in overall cancer risk; however, the effects of the drug combined with testosterone therapy on the risk of hormone-related cancers, are unclear.

Does this medication reduce risk of cancer?

David S. Lopez, DrPH, an associate professor of epidemiology at The University of Texas Medical Branch (UTMB) in Galveston, and colleagues identified 143,035 men aged 65 and older in the Surveillance, Epidemiology, and End Results (SEER) Medicare 2007-2015 database who had been diagnosed with incident prostate, colorectal, or male breast cancer.

Among the men, 110,430 were identified as White, 13,520 as Black, and 19,085 as another race, including Asian, Hispanic, or Native American. Their mean age was 75 years, and median time from cancer diagnosis to death or study end was 5.5 years.

Prediagnosis prescription data showed that about 18% of the men had been treated with metformin alone, 1.5% with testosterone alone, and 0.5% with testosterone and metformin.

The analysis showed that metformin and testosterone replacement therapy were independently and jointly associated with a reduced incidence of prostate cancer, with the greatest reduction with the combination of the two (joint odds ratio [OR],  0.44).

Metformin and testosterone replacement therapy were also independently and in combination inversely associated with the incidence of colorectal cancers (joint OR, 0.47)

There were no significant associations between metformin and testosterone replacement therapy use and mortality with any of the cancers assessed.

Overall, the findings show independent and inverse associations between prediagnostic use of metformin and testosterone replacement therapy with incident prostate and colorectal cancers and in older men, including stage and grade at diagnosis. More studies are needed to confirm these associations independent and joint therapy. 


David S. Lopez,Ioannis Malagaris,Efstathia Polychronopoulou,Konstantinos K. Tsilidis,Sadaf A. Milani,M. Kristen Peek,Alejandro Villasante-Tezanos,Laith Alzweri,Jacques Baillargeon (July 28, 2022). Metformin and testosterone replacement therapy inversely associated with hormone-associated cancers (prostate, colorectal and male breast cancers) among older White and Black me. Clinical Endocrinology. Retrieved from : 


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