Varicocele and male infertility: Part II: The pathophysiology of varicoceles in the light of current molecular and genetic information

Varicoceles are a common cause of male infertility, but despite data being obtained from animal models and human studies the pathophysiology remains unclear. Recently, molecular and genetic information has been reported on men with varicoceles which may shed new light onto the causes of decreased semen parameters and poor sperm function. Here, a number of studies are reviewed in an attempt to develop a working hypothesis for the relationship of varicoceles and infertility. New studies on testicular tissue of men with varicoceles have demonstrated increased apoptosis among developing germ cells, which may be the cause of oligospermia. Other studies with semen have shown increased levels of reactive oxygen species (ROS) in association with poor sperm motility. Recent studies of morphologically abnormal spermatozoa have demonstrated disruption of the sperm head actin by cadmium, a cation reported to be present in high concentrations among some men with varicoceles. Finally, microdeletions of the alpha-1 subunit of the sperm calcium channels in a proportion of men with varicoceles suggests a genetic defect leading to abnormal acrosomal function. The intent of this review was to explain the pathophysiology of varicoceles, and the findings seem to support a 'co-factor' hypothesis. In order for varicoceles to be associated with infertility, they exist as 'co-factors' along with other molecular/genetic problems.