I’m curious about who they measured. We already know that the US population of 30 year olds has roughly half the testosterone of their grandpas at the same age. If you’re only measuring the sick, so to speak, you might not find anything.

For anyone down voting, an open question in the paper is “do Asians have factors that might mitigate the phytoestrogens?” They don’t know.

As to evidence that levels are dropping, https://www.healio.com/endocrinology/hormone-therapy/news/pr...