Vulnerability of the human Leydig cell to radiation damage is dependent upon age

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Abstract
Testicular function was studied in three groups of patients previously treated for malignant disease, and a control group of adult males. The adult patients in groups one and two underwent unilateral orchidectomy for a testicular tumour but only in group two was this followed by post-operative high-dose irradiation (30 Gy) to the remaining testis. Four of the five boys in group three had a unilateral orchidectomy between the ages of 1 and 4 years and all five received a similar dose of irradiation (27·5–30 Gy) to the scrotum as in group two. The five subjects in group three were studied between the ages of 12 and 34 years. In group one the median basal testosterone level (16·0 nmol/l) was normal and the basal gonadotrophin levels mildly but significantly increased, reflecting a resetting of the pituitary-testicular axis following unilateral orchidectomy. In group two the median basal testosterone level (12·5 nmol/l) was significantly lower and the median basal FSH and LH levels were significantly higher than the respective values in group one, indicating that irradiation to the testis in adult life may damage both the germinal epithelium and the Leydig cells. All five males in group three showed grossly increased FSH and LH levels, with a median basal testosterone level (< 2·5 nmol/l) significantly lower than groups one and two. None of the five showed a testosterone response to a stimulation test with human chorionic gonadotrophin or underwent puberty spontaneously. The severe reduction in testosterone levels in group three compared with group two, despite the similarity of radiation dose received, suggests a much greater vulnerability to radiation-induced Leydig cell damage in the prepubertal boy compared with the adult male. Journal of Endocrinology (1989) 120, 161–165