even a slightly low thyroid can cause problems for some dogs. I also look at transitions from puppy to maturing adult ages. 7 months through 2 or 3 years old I've seen changes in behaviors that are testing their positions defining who they are. It's not set in stone, it's a development learning phase. I give them space /supervision from the triggers, and work towards appropriate behaviors. Then they go into the sweet older adult stages where the petty things don't interest them as much and they have the skills and control to handle them better.