I just wanted to say that a work at a Animal Hospital and so I do alot of the blood test there includng the thyroid tests. The only test we do for it is the T-4. And the My vet says that weight gain and hair loss are syptoms of a thyroid problem and then we test for it using the T-4.

I would get a second opinion from a different vet. I am not saying thyroid problems can't cause aggression problems, but i have never heard of it.

Also I just wanted to say that Hercules is half Aussie and he is pretty aggressive to strangers and children. I never knew that Aussie were considered aggressive. So maybe that explains Hercs behavior. Hercules's brother is the same way.