The seminiferous tubules and the Leydig cells are also sensitive to radiation damage; decreased secretion of testosterone is the result of diminished testicular blood flow. Fractionated radiation may have a more profound effect than single-dose radiation. Recovery of sperm density depends on radiation dosage, and the complete recovery of sperm density may take as long as five years. Permanent infertility can occur after radiation therapy of a malignant Iymphoma, despite the fact that the testes are shielded. Permanent androgen deficiency is uncommon after radiation in adults, but boys who receive direct testicular radiation for acute lymphoblastic leukaemia may have permanently low plasma testosterone levels.
