I have put a few posts on before about my dobe (he is 19 months old now).  He suddenly became quite dominant/aggressive to some dogs (well really only Schnauzers), it was around the 14/15 month stage.  Anyway I spoke to quite a few different people, dog trainers, vet and behaviourist and they suggested that this was sexual aggression and that I should firstly try castration and then consider training again.  I have now had him castrated (last Thursday), at the moment I am just lead walking him until his wound has healed completely.  Does anyone know roughly how long before the testosterone cools down?  I am going to sort out his training classes again this week.  It is a shame really as he doesn't really approach other dogs (he is more interested in his football or ball), but the problem is other dogs approaching him.  In the last couple of months I have just tried to avoid other dogs when we are out, but that is not fun.

Hi there, it can take up to 6 months before the testosterone gets out the system. This site is quite interesting. http://www.gsdhelpline.com/castration.htm
Good luck and I hope this helps.

Its 6 weeks until they are safely non fertile but it does take 6 months for the testosterone levels to drop low enough to see a difference.

Bev

hi, just saw your post and thought I'd respond because my dog was done 6 months ago so I've very recently been through it. In his case - and that of other dogs I know and see a lot of at the moment who've also been done- there were immediate changes that I could see. My dog calmed down a lot. But please don't be surprised or alarmed if the first time you let him off lead he seems a bit hyper and behaviour seems worse. It seems to be common in dogs that I've seen that this happens initially. I personally think it's just a result of being kept on the lead for more time than they'd like. They settle down after a couple of days.

What I've also noticed is that every so often since he was neutered his behaviour reverts back for a few days. It was explained to me that it's because the hormone development doesn't stop completely for six months.  Hope you find it works out for him.
Margaret