This is an expression that describes when miners would carry birds (canaries) down into the mine tunnels with them. If dangerous gases such as carbon monoxide collected in the mine, the gases would kill the canary before killing the miners, thus providing a warning to exit the tunnels immediately
New research suggests that infertility can be the canary in the coal mine for men .
Men with infertility are at higher risk of prostate cancer. In particular, men who needed IVF technology for male factor were more likely to develop prostate cancer and at an earlier age than men who fathered pregnancies naturally. This finding does not mean that fertility treatments themselves raise men’s prostate cancer risk.
Men with infertility should tell their other doctors that they have infertility. Because infertility may be the canary in the coal mine for other medical conditions, including prostate cancer.
Enhancing Fertility 