Gonadal function after testicular radiation for acute lymphoblastic leukaemia.

Pubertal maturation, growth, and gonadal function were assessed in 13 boys with acute lymphoblastic leukaemia who had received direct testicular irradiation three to nine years earlier as treatment for testicular relapse or prophylaxis against this complication. Six boys had reached Tanner stage III-V puberty, five of whom had normal growth velocities and bone ages equivalent to chronological age. One boy exhibited maturational arrest on entering stage IV. The remaining seven children (54%) showed evidence of complete pubertal delay or arrested development in stage II, with absence of the pubertal growth spurt and often with delayed bone age. Basal gonadotrophins were abnormally high in all 13 boys, and those with delayed puberty had prepubertal concentrations of testosterone. Testicular irradiation given before puberty causes permanent Leydig cell damage in a high proportion of subjects, necessitating testosterone supplementation. The extent of damage may be related to the age at which radiation is delivered.