A veterinarian can run tests to see if a dog’s aggression is due to a medical reason.
Aggression in dogs may have a medical basis. Drug-induced aggression can lead to growling, snapping teeth, baring teeth, and placing the body in a dominant position. Medical causes of aggression in dogs include hypothyroidism, hypoglycemia, and brain inflammation.
Brain inflammation that occurs in conditions such as encephalitis is one of the most serious medical causes of aggression in dogs. Rabies and distemper are the two types of viral encephalitis. In cases of brain inflammation from diseases such as encephalitis, the aggression is usually a neurological reaction to the effect of inflammation on the brain.
Hair loss in a dog can be a symptom of hypothyroidism.
Hypoglycemia, or low blood sugar, is another possible cause of aggression and may or may not be related to diabetes. Dogs with low blood sugar levels may feel disoriented and uncomfortable. If they feel vulnerable, they may behave aggressively to avoid appearing weak. Dogs with low blood sugar levels may have glassy eyes and stare. Weakness or collapse may occur. A veterinarian can perform a simple blood test to diagnose hypoglycemia.
Inflammation of the brain can cause aggression in dogs.
Hypothyroidism is one of the most common medical causes of aggression in dogs. Very low thyroid levels affect mood. Thyroid replacement therapy has worked to relieve aggression in hypothyroid dogs in some cases. Weight gain, lethargy, and loss of a large amount of hair are other symptoms of hypothyroidism.
More than 50 different breeds and crossbreeds are susceptible to hypothyroidism, and it is one of the most studied causes of canine aggression. Changes in behavior, especially aggression, are often the first signs of this condition. Even a dog that was once friendly to strangers can become aggressive if he has extremely low thyroid levels. A veterinarian can perform a blood test to diagnose hypothyroidism.
Some dogs may act more aggressively out of fear.
The medical causes of aggression in dogs can sometimes be more subtle than growling and biting. A dog may suddenly start stepping on people’s feet or blocking doors as a way of exercising dominance. Cognitive Dysfunction Syndrome (CDS), sometimes called “Alzheimer’s disease in dogs,” is considered another cause of aggression. CDS can lead to behavioral changes due to brain cell loss caused by brain degeneration.