Testis–gut-reproduction axis. (1) GIH and gut microbiota regulate testicular reproductive function. (2) (+) represents a hormone with protective effects or a microbiota positively correlated with testosterone levels, while (−) represents the opposite. (3) Androgens can also affect the composition of gut microbiota. (4) In the future, further discussions will be conducted on the impact of androgens on GIH, as well as the interaction between gut microbiota and GIH. (5) Reproductive health and gastrointestinal health are closely related, and they interact with each other, which is of great significance in maintaining human health.