Cryptorchidism is the most frequent genital anomaly in male newborns (> 1 per cent). Being small for gestational age seems to be the main risk factor for cryptorchidism. Recent warnings coming from industrialized countries have placed emphasis upon an increasing incidence over the last decades in male reproductive abnormalities (cryptorchidism, hypospadias, and testis cancer) and, on the contrary, a reduction in sperm counts. Testicular cancer, cryptorchidism, hypospadias and poor spermatogenesis are risk factors for each other and it has been hypothesized that they are all signs of a developmental disturbance called testicular dysgenesis syndrome.
Although genetic abnormalities can cause cryptorchidism, in the majority of cases, the reasons remain unclear. Eco-epidemiological studies suggest that environmental factors contribute to the problem. The main hypothesis is that cryptorchidism (like other disorders) is consecutive to exposure of the developing foetus to “endocrine disrupters”. These chemicals with endocrine activity have become a prime importance topic of investigation.
In animals, the level of evidence for an impact of endocrine disrupters on cryptorchidism is high, and biological pathways by which chemicals may disrupt endocrine balance are better identified: various environmental factors hav demonstrated their ability to mimic, antagonise or interfere with androgens and estrogens, or to disrupt the physiological estrogens/androgens balance.
Even if evidence in humans remains limited, recent epidemiological studies improve the level of evidence for an exposure-outcome relation between endocrine disrupters and the occurrence of cryptorchidism.
Further researches focusing on endocrine modulation are desirable, in order to ensure full validation of effects of endocrine disrupters.