Diabetes drug metformin found in freshwater is a potential cause of intersex fish

Public Release: 24-Apr-2015

Fish exposed to metformin were also smaller in size than those not exposed

University of Wisconsin – Milwaukee

A medication commonly taken for Type II diabetes, which is being found in freshwater systems worldwide, has been shown to cause intersex in fish -male fish that produce eggs.

A study by Rebecca Klaper at the University of Wisconsin-Milwaukee determined exposure to the diabetes medicine metformin causes physical changes in male fish exposed to doses similar to the amount in wastewater effluent.

In addition to intersex conditions, fish exposed to metformin were smaller in size than those not exposed, said Klaper, a professor in UWM’s School of Freshwater Sciences.

The study, co-authored by Nicholas Niemuth, a researcher in Klaper’s lab, was recently published in the journal Chemosphere.

Because intersex fish are particularly prevalent downstream from wastewater treatment plants, many studies have investigated the effect of hormones from birth control pills, Klaper said.

Initially, the results of her study seemed surprising since metformin is not a hormone and it targets blood sugar regulation.

But Klaper said it is also prescribed to women with a common hormonal disease called polycystic ovary syndrome. The research in her lab indicates metformin could be a potential endocrine