Leydig cell insufficiency after testicular irradiation for acute lymphoblastic leukemia

Leydig cell function in 21 boys with acute lymphoblastic leukemia who had been treated by bilateral direct testicular irradiation (12 X 2 Gy) at 8.4 +/- 0.7 years, was evaluated 3.8 +/- 0.4 years after irradiation. At the time of irradiation all were prepubertal and at evaluation 12 were prepubertal and 9 pubertal. Leydig cell insufficiency, indicated by a low plasma testosterone response to chorionic gonadotrophin and/or an increase in basal level of plasma luteinizing hormone, was observed in 19/21 patients. The children who were the youngest at testicular irradiation were more vulnerable. Spontaneous virilization occurred in 3 of the older children and resulted from compensated Leydig cell dysfunction.