Declining semen quality and increasing incidence of testicular cancer: is there a common cause?

Male reproduction has been given little attention in science and in medical practice. However, a recent metaanalysis on semen quality, which clearly pointed to a decrease over the past 50 years, has been repeatedly quoted. Three recent reports have found that semen quality has declined among candidate semen donors during the past 20 years. The evidence of decline in the quality of semen is not the only indicator that the human testis is at risk. During the past 50 years, cancer of the testis has also become more common. This is a disorder of young men, and it is associated with a high rate of other abnormalities of the testis including undescended testis and poor semen quality. Furthermore, the incidence of both hypospadias and undescended testis has been reported to be rising in the general population. We believe that the evidence of declining semen quality should be seen in the light of these trends in other reproductive disorders of men. However, the etiology is unknown. A recent hypothesis that links the trends in the health of the male reproductive system to xenoestrogens in the environment is discussed.