One of the major side effects of cyclophosphamide (Cytoxan) in both men and women is gonadal failure and resultant infertility. While there is markedly less risk with the doses typically used for the treatment of glomerular disease than, say, the massive doses used for chemotherapy, there is still a concern that long-term exposure to Cytoxan can have fertility implications.
One potential strategy to minimize the risk of infertility in women is to use the hormone leuprolide, a gonadotropin release hormone (GnRH) agonist. The idea here is that although leuprolide initially triggers a surge in LH & FSH, prolonged exposure leads to decreased LH & FSH levels, and this will eventually result in oocyte quiescence. There is some data to support its use in the delaying of premature ovarian failure in women with lupus with long-term Cytoxan exposure in this paper by Somers et al. Of note, it typically takes several weeks for leuprolide to work, so it is not necessarily a good option in individuals with rapid renal deterioration in whom starting Cytoxan is a priority.
In men, the risk of infertility with Cytoxan is less well-defined than with women, but sperm banking may be a convenient option.