Well then if there's only estrogen in the brain, we must all think like women...I'll remember this next time my wife tries to tell me that women are mentally superior

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And actually the presence of testosterone affects the development of the brain, they have experimented with making 'male' and 'female' brained mice in both biological genders of mice successfully. Never heard of testosterone being converted into estrogen on its way to the brain. Perhaps it becomes toxic after the development cycle or it is converted into another substance that affects the brains development? I'm not a neurologist so I couldn't tell you.
Blood itself is also toxic to the brain

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