Effect of irradiation treatment on gonadal function in men treated for germ cell cancer.

Irradiation may have a profound effect on reproductive function. The schedule of the delivered irradiation (total dose, number of fractions and duration) is an important determinant of the radiobiological effect on the tissues involved and varies between different tissues and organs. Direct irradiation to the testis will, in lower doses, affect the germinal epithelium: doses of irradiation greater than 0.35 Gy cause aspermia which may be reversible. The time taken for recovery increases with larger doses, however, with doses in excess of 2 Gy aspermia may be permanent. At high radiation doses (> 20 Gy) Leydig cell function will also be affected.