What Are the Signs of Hypothyroidism in Dogs?

Hypothyroidism is a common endocrine disorder in dogs that impacts the thyroid gland's ability to produce hormones essential for regulating metabolism and energy. An underactive thyroid can lead to various symptoms that may significantly affect your dog’s health and quality of life. Recognising hypothyroidism early is key to helping your dog receive timely treatment and stay as healthy and comfortable as possible.

In this article, we’ll cover the causes of hypothyroidism in dogs, the symptoms to watch for, and what to do if you suspect your dog may be affected.

What Causes Hypothyroidism in Dogs?

The two main underlying causes of hypothyroidism in dogs are:

1. Autoimmune Thyroiditis: Also known as lymphocytic thyroiditis, this is when the immune system mistakenly attacks and damages the thyroid gland, reducing its ability to produce hormones.
2. Idiopathic Thyroid Atrophy: This is a natural decrease in thyroid tissue, where the thyroid gland shrinks for unknown reasons. This process is also associated with a reduction in thyroid hormone production.

Breeds Commonly Affected by Hypothyroidism

While hypothyroidism can occur in any breed, some are more prone to developing the condition, including:

• Golden Retrievers
• Labrador Retrievers
• Doberman Pinschers
• Boxers
• Cocker Spaniels
• Dachshunds

In general, larger breeds may be at a higher risk for hypothyroidism, although any breed, size, or mixed-breed dog can develop the condition.

Recognising the Signs of Hypothyroidism

The symptoms of hypothyroidism in dogs can develop gradually, often mimicking signs of ageing or other health issues. Here are some of the most common signs to watch for:

1. Unexplained Weight Gain

One of the hallmark signs of hypothyroidism in dogs is gradual weight gain, despite no changes in food intake or diet. Since thyroid hormones help regulate metabolism, a deficiency causes the body to slow down, leading to excess weight over time.

2. Lethargy and Decreased Activity

Dogs with hypothyroidism often show reduced enthusiasm for activities they once enjoyed, appearing sluggish or fatigued. They may sleep more and lose interest in exercise or play. This reduced energy level is sometimes mistaken for normal ageing, but it’s worth considering if a health issue like hypothyroidism might be the cause.

3. Changes in Coat and Skin

Hypothyroidism can cause noticeable changes in a dog’s coat and skin. Affected dogs often have a dull, brittle coat and shed excessively. Fur thinning around the flanks, back, and tail (sometimes referred to as a “rat tail” appearance) is common. Additionally, the skin may become thick, dry, or flaky, and dogs with hypothyroidism may develop recurring skin infections or hot spots.

4. Cold Intolerance

Dogs with hypothyroidism often become more sensitive to cold temperatures as their metabolism slows down. You may notice your dog seeking out warmer places to rest, shivering more frequently, or seeming uncomfortable in cooler weather.

5. Behavioural Changes

Hypothyroidism can also affect a dog’s mood and behaviour. Affected dogs may appear withdrawn, depressed, or anxious, while some may even show irritability or, in rare cases, aggression. Behavioural changes are less common but can provide additional clues for diagnosis.

6. Bradycardia (Slow Heart Rate)

An abnormally slow heart rate, or bradycardia, can also indicate hypothyroidism. Your veterinarian may detect this during a physical examination. If your vet notes a slow heart rate, they may recommend testing for thyroid function to assess for hypothyroidism.

7. Neurological Symptoms (Rare)

In rare cases, hypothyroidism may cause neurological symptoms, such as muscle weakness, a head tilt, dragging of the feet, or even facial paralysis. Some dogs with severe hypothyroidism may experience unsteadiness or even seizures. These symptoms are uncommon but can signal a more advanced or untreated thyroid issue.

What Should You Do If You Notice These Signs?

If your dog exhibits any of these symptoms, it’s important to consult your veterinarian. Since hypothyroidism shares symptoms with other conditions such as diabetes, Cushing’s disease, and obesity, an accurate diagnosis is essential.

Step 1: Physical Examination and Medical History

When you bring your dog to the vet, they will conduct a thorough physical examination and discuss your dog’s behaviour, diet, and activity levels. Providing as much information as possible can help the vet determine whether hypothyroidism may be the cause of your dog’s symptoms.

Step 2: Blood Tests

Blood tests are the primary diagnostic tool for hypothyroidism. Your veterinarian will typically measure your dog’s levels of T4 (thyroxine) and TSH (thyroid-stimulating hormone). Low levels of T4 and elevated TSH levels are often indicative of hypothyroidism, although further testing may be recommended for confirmation.

Step 3: Further Testing if Needed

If initial tests are inconclusive or suggest other potential health issues, your veterinarian may recommend further diagnostic testing. Additional tests could include urinalysis, abdominal ultrasound, or more specialised hormone tests to rule out other conditions with similar symptoms.

Treatment for Hypothyroidism in Dogs

Once a diagnosis of hypothyroidism is confirmed, the condition is usually managed with daily thyroid hormone replacement therapy. The medication is generally well-tolerated by dogs and will likely be required for the rest of your dog’s life. However, with proper treatment, most dogs with hypothyroidism can live healthy, active lives.

When to Reach Out for Help

Even with consistent treatment, it’s essential to monitor your dog for any recurring or worsening symptoms. Changes in weight, energy, or coat quality can indicate the need for a dosage adjustment. Regular check-ups with your veterinarian and careful observation of your dog’s behaviour and health are key to managing hypothyroidism effectively.

Final Thoughts

Hypothyroidism in dogs can be a concerning diagnosis due to the broad range of symptoms it produces. However, with early detection and appropriate treatment, hypothyroidism can be effectively managed, allowing your dog to live a comfortable and fulfilling life. By staying aware of the signs of hypothyroidism and seeking prompt veterinary care, you can ensure your pet receives the care they need.

If you suspect your dog may be showing signs of hypothyroidism, don’t hesitate to reach out to your veterinarian. With proper management, your dog can lead a happy and healthy life, even with this condition.