Hormone treatment after irradiation stimulates recovery of rat spermatogenesis from surviving spermatogonia.

The possibility of stimulating the recovery of spermatogenesis after irradiation using hormone treatment was tested in LBNF, rats. At 10 weeks after irradiation with 3.5 Gy, the percentage of tubules showing recovery of spermatogenesis (repopulation index) was 37% in rats that received no hormone treatment. GnRH agonist (GnRH-Ag) treatment with Zoladex or continuous treatment with testosterone markedly stimulated the recovery of spermatogenesis. When GnRH-Ag treatment was started immediately after 3.5-Gy irradiation and maintained for 10 weeks, the repopulation index was 91%. When an additional 6.5 weeks without further treatment was allowed between the 10-week GnRH treatment and killing the rats, the repopulation index recovered to 100% and sperm counts to 83 x 10(6). These sperm counts were more than 100-fold higher than those in rats not given hormone treatment and 50% of normal nonirradiated control levels. GnRH-Ag for 10 weeks also stimulated spermatogenic recovery in rats irradiated with 6 Gy, even when the start of treatment was delayed until 18 weeks after irradiation. Without GnRH-Ag, the repopulation index was 0, but in GnRH-Ag-treated rats it was 14.5%. Since all of the hormone treatments suppress intratesticular testosterone, high levels of testosterone may be inhibiting differentiation and their suppression may stimulate recovery. Even though the exact mechanism is not yet known, this method may still be applicable for clinical use to activate spermatogenesis in patients rendered azoospermic by irradiation or possibly by other cytotoxic treatments.