Hypothyroidism in dogs may cause which behaviors?

• A. Lethargy and obesity
• B. Excessive barking
• C. Deafness
• D. Aggression and anxiety

Answer: (D)

Thyroid hormones influence brain function and mood, so when a dog becomes hypothyroid, behavioral changes can occur. A slower metabolic state and CNS effects can lead to changes in how a dog feels and reacts, including increased anxiety and irritability. In some cases, these mood alterations may manifest as aggression, especially if the dog becomes more tense or less tolerant of handling or new situations. The other options describe physical signs (lethargy, obesity) or less typical behavioral triggers (excessive barking, deafness) that aren’t as directly linked to hypothyroidism. So the behavior-related change most consistent with hypothyroid effects is aggression and anxiety.