Hypothyroidism is the most common hormone imbalance of dogs, but usually only affects mid to large size breeds. The most susceptible breeds appear to be the Doberman Pinscher, Irish Setter, and Golden Retriever. Other breeds with a high incidence are Cocker Spaniel, Dachshund, Boxer, and Airedale Terrier.
Symptoms typically appear between the ages of 4 and 10, but once a diagnosis is made, treatment will last for the remainder of the dog’s life. The most common symptoms of hypothyroidism in dogs is loss or thinning of fur, dry coat, excessive shedding, lethargic behaviour, weight gain or obesity, anemia, and thickening of tissues, typically of the face and head. This skin thickening can lead to skin folds sometimes referred to as ‘tragic face’. Some dogs suffering from hypothyroidism will have frequent ear infections, ear pain, redness and odor. Skin infections may develop that are itchy and can result in sores on the rest of the body.
Diagnosing hypothyroidism is a bit more difficult than just taking a blood sample. Since there are fluctuating levels of thyroid hormones at any given time, a routine blood test may not catch it. A panel of blood tests can typically confirm a suspected diagnosis of hypothyroidism.
Treatment of oral hormone replacement will typically begin at twice-daily intervals until the dog’s coat shows signs of improvement, and then once a day medication after that. It usually is within the first 6 weeks of treatment that regrowth of fur becomes noticeable.