I read somewhere once that the most common age for dogs to be turned into the shelter was around 9 months because they lose their minds. My terrier did the same thing- I swear he forgot “down” the night he was graduating from one of his obedience classes!
Anyway, I bet it’s the age more than the hormones. The recommendation is starting to change from earlier to later in males, with some saying if they are nice and have good manners then you don’t really need to neuter if you can prevent them from getting loose and impregnating something. Even the potential problems (prostate, testicular cancer, etc.) can often be corrected by neutering if they happen.
I was on the fence with my most recent dog (now 3 1/2 yrs). He was great, but I finally neutered him at 22 months - he was REALLY distracted in agility two different nights (there were girls in heat, so I don’t blame him), he was starting to get snarky with a friend’s neutered male (he loved the friend’s spayed female), and the final straw- he was “aggressively humping” his friends at doggie daycare. Neutered him the next week and after about 30 days, he was back to great. 