Leydig cells are more resistant to damage from radiotherapy than is the germinal epithelium. Significant rises in LH have been demonstrated after single dose radiation doses of above 0.75 Gy (6) and fractionated doses above 2 Gy (40). However, no change in testosterone level was seen at these doses, and LH values gradually return to normal levels during 30 mo. Higher testicular radiation doses do, however, result in more marked Leydig cell insufficiency. Giwercman et al. (41) studied 20 men who were previously treated with unilateral orchidectomy for testicular cancer, who received direct testicular irradiation at a dose of 20 Gy, in 10 fractions, for carcinoma in situ in the remaining testis. A significant increase in mean LH levels was observed in the first 3 mo (10.4 to 15.6 IU/L), with a decrease in mean serum testosterone level (13.3 to 10.8 nmol/L). Similar results were observed by Shalet et al. (7) in adults treated with highdose (30 Gy) testicular irradiation after unilateral orchidectomy. Serum testosterone levels were significantly reduced (12.5 vs 16.0 nmol/L), and LH levels significantly increased (16 vs 6 IU/L), compared with a control group who had undergone unilateral orchidectomy without subsequent radiotherapy. In addition, more marked abnormalities were observed in a group of five adult men treated with the same testicular dose of irradiation during childhood. Median LH level was greater than 32 IU/L, and median testosterone level was less than 2.5 nmol/L, and there was no response to a human chorionic gonadotrophin (hCG) stimulation test, suggesting that the prepubertal testis is much more vulnerable to radiation-induced Leydig cell damage.
Was this article helpful?