What has happened to the male reproductive system?

The health of the male reproductive system deteriorated sharply during the twentieth century. Testicular cancer increased four-fold or more in the space of several decades, throughout the world in populations of European ancestry, and in certain others, e.g. Maoris in New Zealand (Adami et al., 1994; Joffe, 2001; Parkin, 2005). There is pathological evidence that the disease process starts in early life (Skakkebaek et al., 1987), and in accordance with this the time trends show the clearest patterns if looked at by birth cohort, e.g. the incidence stopped increasing for ten years around 1940 in Denmark, Norway and Sweden (but not Finland, East Germany or Poland), then resumed its rapid rise (Figure 2.1)(Bergström et al., 1996). The increase started in men born in the late nineteenth century in England and Wales (Davies, 1981), and in the first decade of the twentieth century in the Nordic countries, Germany and Poland (Bergström et al., 1996). Many features of the epidemiological data are consistent with risk being associated with increasing prosperity.

Paradoxically, although testis biology is extremely well conserved through evolution, there is no satisfactory animal model for this disease, so the evidence is limited to epidemiological studies, genetic studies and clinical research (Skakkebaek, 2007). These are complicated by the existence of two main types of testicular cancer: seminoma and non-seminoma (divided into embryonal cell carcinoma, teratoma, choriocarcinoma and mixed-cell type).