[Spermatogenesis after fractionated, low-dose irradiation of the gonads ].

58 patients (50 retrospectively, 8 prospectively) who received post-operative radiotherapy for seminoma, constitute the patient population with which the tolerance dosage for spermatogenesis following low-dose fractionated radiation of the gonads was determined. Field arrangement and caudal field limit were the parameters which determined the amount of the dose to the gonads. Total doses of less than 100cGy, with daily doses of 3 to 5 cGy, permit a complete recovery of spermatogenesis within 14 to 22 months. The occurrence of an azoospermia can be expected 3 to 5 months after initiation of irradiation, lasting for 5 to 6 months. Doses of more than 100 to 150 cGy permit only partial recovery of spermatogenesis and doses of more than 150 cGy can lead to permanent azoospermia. In the absence of evidence of mobile spermatozoa in the ejaculate more than 2 years after radiotherapy, no repopulation of the seminiferous tubules can be expected. After receiving ionizing radiation, the stem cells of the spermatogonia have only a very limited capability for repair, regeneration and compensation. This is the reason for the very high sensitivity of the spermatogenesis to low-dose fractionated radiation of the male gonads.