Men who take finasteride (brand name Proscar) or the closely related dutasteride (Avodart) for an enlarged prostate should be monitored for type 2 diabetes, because these drugs increase the risk of this disease, according to a study published in April 2019 in the journal BMJ.
In the study, researchers analyzed data from about 55,000 British men who were taking the drugs or a third, unrelated prostate drug, tamsulosin, to treat their urinary symptoms. Over an 11-year period, men taking finasteride or dutasteride were about 30 percent more likely to develop diabetes than those taking tamsulosin. Results were similar when the researchers looked at a Taiwanese health database.
Type 2 diabetes is caused by insulin resistance, which is a reduced sensitivity of the body’s tissues-primarily the liver and muscles-to the action of insulin coupled with a progressive reduction in the ability of pancreatic beta cells to produce insulin.
It’s theorized that finasteride and dutasteride affect metabolism in ways that reduce insulin sensitivity and increase fatty liver. In absolute numbers, if 1,000 men take the drugs for a decade, about 16 extra cases of diabetes would develop.
In addition to monitoring such men for diabetes, health care providers should counsel them on diet, exercise, and weight control to help mitigate this risk, the authors advised.