11-Ketotestosterone (11-KT) is an androgenic steroid hormone primarily studied in fish, where it is recognized as a major androgen responsible for the development and maintenance of male secondary sexual characteristics, spermatogenesis, and reproductive behaviors. In teleost fish species, 11-KT is often the predominant androgen in males, surpassing testosterone in activity and circulating levels. Numerous studies have documented that 11-KT administration can stimulate testicular development, increase sperm production, and induce male-typical reproductive behaviors in fish. These effects are supported by both in vivo and in vitro experiments across several fish species, making 11-KT a well-validated marker and tool in aquaculture and fish physiology research.

However, in mammals—including humans—the physiological role of 11-KT is much less significant. While 11-KT is present in human plasma as a metabolite of adrenal steroids, its androgenic effects are relatively weak compared to testosterone and dihydrotestosterone (DHT). There is limited research on its use or efficacy in supporting the human male reproductive system, and it is not commonly used clinically for this purpose. Therefore, while the scientific evidence for 11-KT supporting the male reproductive system is robust in fish, it does not extend meaningfully to humans or other mammals.

In summary, 11-KT is scientifically validated as a key androgen for male reproductive function in fish, but there is little to no evidence for its use in supporting the human male reproductive system.