I am not an expert on biochemistry, just an unlucky user of finasteride who is experiencing sexual side effects.
Here is the theory: fin affects everyone in the same way, i.e. by inhibiting the DHT receptors in some way, so the only people reporting problems are those whose sexual functions “rely” on DHT more than on testosterone.
Everybody is(was) different (note that I’m talking about our “pre-finasteride era”): there are people who need to have an orgasm once or more a day, and people who are fine with twice a week; there are people who have long lasting erections no matter what and people who, after making out for 10 minutes, would get a soft if the sexual stimulus was interrupted for 30 seconds (for example if you have to get up and get a condom).
Is it possible that those who (for example) are used to have long erections rely a lot on DHT, and therefore are more affected by fin? Suppose that my penis gets hard almost only through testosterone (since everybody is different, this is actually possible) . Then I would not notice finasteride side effects because I normally don’t use my DHT receptors. And if I had a brain fog or other symptoms that are not related to my sexual functions, I would unlikely relate them to finasteride, just because this poison is mainly known to give sexual side effects.
I’ll just throw an idea here: what about creating a poll where post-finasteride sufferers answer a few questions about their sex life, just to see if there is some common characteristic that post-finasteride sufferers share?