https://www.sciencedirect.com/science/article/pii/S0890623820302926
Reproductive Toxicology - Volume 100, March 2021, Pages 60-67
Clinical data were analyzed to examine effects of soy/isoflavones on hormone levels.
38 clinical studies were deemed suitable for inclusion in the meta-analysis.
No effects of soy/isoflavones on testosterone or estrogen levels in men were noted.
... extensive clinical data published over the past two decades shows that in men neither soy nor isoflavone intake, even when exposure occurs for an extended period of time and exceeds typical Japanese intake, affects levels of total testosterone, free testosterone, estradiol or estrone.