That hormone is testosterone. And that means that no matter how much testosterone those people with Y chromosome(s) get, their body cannot use them. Hence, they

That hormone is testosterone. And that means that no matter how much testosterone those people with Y chromosome(s) get, their body cannot use them. Hence, they have a disadvantage even in women sports. In theory. The problem is that for example in women boxing these people are overrepresented. This indicates that testosterone is possibly not the only answer, and we don’t know the full picture AFAIK. But of course it’s also possible that simply Y chromosome causes changes in behavior and not physical performance, and it’s more likely that they like boxing more. We don’t know. The current best proven differentiator AFAIK is testosterone level and whether their body can process that.