Does a testicular dysgenesis syndrome exist?

The concept of an increasingly common Testicular Dysgenesis Syndrome (TDS) has been widely adopted with little epidemiological appraisal. In this paper we critically review the epidemiologic evidence of the existence of a non-genetic TDS. We systematically assess and discuss the evidence of all six possible associations between the four defining conditions of TDS: impaired spermatogenesis, undescended testis, hypospadia and testicular cancer. We also evaluate whether there are common risk factors for these four conditions. We conclude that epidemiologic studies provide little support for existence of a widespread TDS because there are no consistent non-causal associations between its different manifestations. There is furthermore little evidence of shared causes between the alleged components of the syndrome.