ROTT N CHATTER, August 1992, Volume 1 Number 1 AGGRESSIVE FOR NO REASON? Has your favorite Rottie been a little cranky lately when there really didn't seem to be a reason? Well, you might want to have his or her thyroid level checked. It seems that recent case studies have show a direct link between thyroid dysfunction and aggression. Dogs normally quite even tempered and non-aggressive displayed various levels of unprovoked aggression whenever their thyroid levels varied in the low to below normal range. One dog suddenly began acting quite fearful. This unexplained behavior preceded his biting a child in the family. The owners thought the dog had a vision problem, but after confirmed hypothyroidism, and giving the dog thyroid supplements, the dog's behavior returned to normal. So, when your Rottie reacts aggressively for no apparent reason, make sure it is not a medical problem.