Sudden changes in behavior

Question
I have a boxer bitch that is 2 years old.  She has suddenly become nervous.  She is spooked by sudden noises ( she never was before ).  She is also shying away from some judges during inspection at a show.  Last weekend she even went as far as to growl at the judge.  She has been shown many times before and never had a problem.  Some one told me this could be a Thyroid problem, is that possible?? Is there anyother possible explanation?
Thank You for your time!
Donna

Answer
I would recommend having blood work checked to be on the safe side--CBC, Chem and T4--as well as a urine specimen in case she has an underlying UTI.  I don't really have an explanation for her behavior--some of it may be hormonal.  You can try giving her a valerian root capsule or rescue remedy to see if that helps her.