The 10 boys with normal FSH and LH concentrations included 8 who were given TBI for acute lymphoblastic leukemia (n = 2), acute myeloid leukemia (n = 5), and chronic myelogenous leukemia (n = 1), one who was given TLI for severe aplastic anemia, and one who was given chemotherapy alone (aracytine and busulfan) at one year for acute lymphoblastic leukemia. The gene discussed is PLOD1; the disease is idiopathic aplastic anemia.