HORMONAL-STIMULATION OF THE RECOVERY OF SPERMATOGENESIS FOLLOWING CHEMOTHERAPY OR RADIOTHERAPY - REVIEW ARTICLE

Radiation and chemotherapeutic drugs produce prolonged depression of s perm counts in rodents and humans. Previously, three approaches have b een developed in experimental animals that have had some success in pr eventing or reversing this toxicity. These approaches included pretrea tment with hormones that suppress spermatogenesis, stimulation of stem cell number, and supplementation with testosterone. A different ratio nale for the ability of particular hormonal treatments to reverse prol onged azoospermia is presented in this review. In many cases prolonged azoospermia occurs even though the stem spermatogonia survive the tox ic insult, but the differentiation of these spermatogonia to produce s perm fails. In the rat, the block appears to be at the differentiation of the A spermatogonia. Hormone treatments with testosterone or with GnRH agonists, which suppress intratesticular testosterone levels, rel ieve this block and result in the production of differentiating cells. When the hormone treatment is stopped the production of differentiati ng cells continues, mature sperm are produced, and fertility is restor ed. If a similar mechanism can be demonstrated to hold in humans, the fertility of men who have been rendered infertile by treatments for te sticular and other cancers could be improved.