Defects that cause infertility in the presence of normal androgen production include varicocoele, which occurs in ten to fifteen per cent of the general population and may be a contributory factor in one-third of cases of male infertility. It is caused by retrograde flow of blood into the internal spermatic vein, which eventuates in progressive, often palpable dilatation of the peritesticular plexus of veins (Fig. 11.37). Some ten per cent of men with azoospermia and germinal cell aplasia (the Sertoli cell-only syndrome) have a positive family history and may constitute a specific entity; plasma testosterone and LH levels are normal, and the plasma FSH level is high.
