“Follicle-Stimulating Hormone Treatment for Male Factor Infertility”, Ettore Caroppo, Craig S. Niederberger2022-12-05 (biology)⁠:

Follicle-stimulating hormone (FSH) treatment has been proven effective in stimulating spermatogenesis and improving the reproductive ability of men with hypogonadotropic hypogonadism, while the usefulness of such a treatment in infertile patients with normal pituitary function is restricted to a subgroup of responders that, however, cannot be identified by the current diagnostic tools before treatment. In this review we summarize the role played by FSH in the modulation of spermatogenesis, the effect of FSH treatment at a standard replacement dose and at higher dose on sperm parameters, spontaneous and in vitro fertilization pregnancy rates, and the efforts made to identify possible responders to FSH treatment.

…Sperm parameters and spontaneous as well as IVF pregnancy rates in a subgroup of patients with oligozoospermia can be improved by FSH administration, which seems to exert a stimulatory effect on spermatogenesis even in patients with severe spermatogenic dysfunction, such as patients with NOA. However, the studies performed in the past 30 years, owing to the different study designs, treatment formulations, and primary outcome measures, are not sufficient to provide conclusive evidence about how to identify the possible responders to treatment. The ideal dosage and duration for FSH administration to promote effective stimulation of spermatogenesis in men with infertility requires ongoing and future well-designed clinical trials.