TY - JOUR

T1 - Hypothesis

T2 - Metformin is a potential reproductive toxicant

AU - Tavlo, Maja

AU - Skakkebæk, Niels E.

AU - Mathiesen, Elisabeth R.

AU - Kristensen, David M.

AU - Kjær, Kurt H.

AU - Andersson, Anna-Maria

AU - Lindahl-Jacobsen, Rune

PY - 2022

Y1 - 2022

N2 - Metformin is the first-line oral treatment for type 2 diabetes mellitus and is prescribed to more than 150 million people worldwide. Metformin's effect as a glucose-lowering drug is well documented but the precise mechanism of action is unknown. A recent finding of an association between paternal metformin treatment and increased numbers of genital birth defects in sons and a tendency towards a skewed secondary sex ratio with less male offspring prompted us to focus on other evidence of reproductive side effects of this drug. Metformin in humans is documented to reduce the circulating level of testosterone in both men and women. In experimental animal models, metformin exposure in utero induced sex-specific reproductive changes in adult rat male offspring with reduced fertility manifested as a 30% decrease in litter size and metformin exposure to fish, induced intersex documented in testicular tissue. Metformin is excreted unchanged into urine and feces and is present in wastewater and even in the effluent of wastewater treatment plants from where it spreads to rivers, lakes, and drinking water. It is documented to be present in numerous freshwater samples throughout the world - and even in drinking water. We here present the hypothesis that metformin needs to be considered a potential reproductive toxicant for humans, and probably also for wildlife. There is an urgent need for studies exploring the association between metformin exposure and reproductive outcomes in humans, experimental animals, and aquatic wildlife.

AB - Metformin is the first-line oral treatment for type 2 diabetes mellitus and is prescribed to more than 150 million people worldwide. Metformin's effect as a glucose-lowering drug is well documented but the precise mechanism of action is unknown. A recent finding of an association between paternal metformin treatment and increased numbers of genital birth defects in sons and a tendency towards a skewed secondary sex ratio with less male offspring prompted us to focus on other evidence of reproductive side effects of this drug. Metformin in humans is documented to reduce the circulating level of testosterone in both men and women. In experimental animal models, metformin exposure in utero induced sex-specific reproductive changes in adult rat male offspring with reduced fertility manifested as a 30% decrease in litter size and metformin exposure to fish, induced intersex documented in testicular tissue. Metformin is excreted unchanged into urine and feces and is present in wastewater and even in the effluent of wastewater treatment plants from where it spreads to rivers, lakes, and drinking water. It is documented to be present in numerous freshwater samples throughout the world - and even in drinking water. We here present the hypothesis that metformin needs to be considered a potential reproductive toxicant for humans, and probably also for wildlife. There is an urgent need for studies exploring the association between metformin exposure and reproductive outcomes in humans, experimental animals, and aquatic wildlife.

KW - metformin

KW - reproductive toxicant

KW - testosterone

KW - endocrine disruptor

KW - environment

KW - wildlife

KW - development

KW - ENDOCRINE DISRUPTION

KW - SEX-RATIO

KW - EXPOSURE

KW - MECHANISMS

U2 - 10.3389/fendo.2022.1000872

DO - 10.3389/fendo.2022.1000872

M3 - Journal article

C2 - 36339411

VL - 13

JO - Frontiers in Endocrinology

JF - Frontiers in Endocrinology

SN - 1664-2392

M1 - 1000872

ER -