21 Dec Hypothyroidism and Hyperthyroidism in Dogs (Part 1)

The thyroid gland is located in the dog’s neck, producing thyroxine (T4) and other thyroid hormones. These hormones play a significant role in a dog’s metabolism and can cause many problems if not created at normal levels. The pituitary gland controls thyroid function. Hypothyroidism in dogs is more common in 4- to 10-year-old dogs. This disease is more common in large breeds, and this disorder is rare in small breeds. Stay tuned to learn more about this disease.

Differential diagnosis of hypothyroidism and hyperthyroidism in dogs

Suppose the thyroid gland is overactive (hyperthyroidism), the body’s metabolism increases. If the thyroid gland is underactive (hypothyroidism), metabolism slows down. These two disorders are among the most common diseases. Metabolic disorders are a sign of thyroid disease. The thyroid gland regulates the body’s metabolism. Therefore, thyroid health is essential for maintaining a healthy body.

Hyperthyroidism in dogs

Hyperthyroidism in dogs occurs when the dog’s body produces too much thyroid hormone, causing the dog’s metabolism to reach dangerous levels. It’s rare in dogs and more common in cats, but it’s a severe disease if it occurs in dogs.

One of the primary causes of hyperthyroidism is cancer called carcinoma (thyroid cancer). As soon as the disease is diagnosed, the veterinarian begins treatment based on the stage of cancer, the size of the tumour, and the size of the tissue involved. There are several treatments for hyperthyroidism in dogs, including surgery, chemotherapy, or radiation therapy; The veterinarian selects the appropriate medicine based on the dog’s condition and the cause of the disease. Until then, it can balance hormone levels to some extent with medication. The most common cause of hyperthyroidism is invasive cancer, unfortunately fatal. In this case, the choice of treatment depends on the size of the tumour and its spread in the body. Treatment may include surgical removal of part of the tumour or removal of the entire thyroid gland. The sooner treatment is started, the better the result.

Symptoms

• Weight loss
• Hyperactivity
• Increased appetite and thirst
• Enlarged thyroid gland
• Diarrhea and vomiting
• Increased urination and defecation
• Tachycardia (increased heart rate)
• Heart failure
• Cardiomyopathy (enlarged heart)
• Dyspnea (shortness of breath).
• Usually, the dog owner feels a lump in his dog’s neck.
• Tangled appearance

• Reduce sleep and rest
• Heart murmur

• Galloping heart rhythm
• Increased panting
• Fast breathing
• Depression and weakness (in some dogs)

Hypothyroidism in dogs

A lack of thyroid hormone causes hypothyroidism. The disease is diagnosed with clinical features such as lethargy, weight gain, obesity, hair changes, and low serum thyroid hormone concentrations. Treatment for this disorder includes daily thyroid hormone replacement. This replacement is done with the help of certain drugs.

In fact, in hypothyroidism, a disorder in the production and secretion of thyroid hormones leads to a decrease in the body’s metabolism. The disease is more common in dogs but rarely in other species, including cats, horses, and large pets. Therefore, it is better to find out about this disorder if you have a dog.

Causes

Hypothyroidism in dogs is usually caused by one of two diseases:

• Lymphocytic thyroiditis
• Idiopathic atrophy of the thyroid gland

Lymphocytic thyroiditis is the most common cause of hypothyroidism and is an immune-mediated disease. It means that the immune system suspects that the thyroid is abnormal or external tissue attacking it. It isn’t clear why this is happening. However, this disorder is an inherited disease. It means that genetics play a significant role in its occurrence. In idiopathic atrophy of the thyroid gland, normal thyroid tissue is replaced by adipose tissue.

These two diseases cause hypothyroidism in more than 95% of sick dogs. Another 5 percent develop hypothyroidism due to rare diseases such as thyroid cancer.

Diagnosis

The most common screening test for hypothyroidism in dogs is a measurement of total thyroxine (TT4) levels. This test involves measuring the primary thyroid hormone in a blood sample. Low levels of total thyroxine, often accompanied by clinical signs, indicate hypothyroidism.

The dog is then definitively diagnosed with hypothyroidism by performing a T4 with equilibrium dialysis (T4 by ED) or a thyroid panel that assesses the level of multiple forms of thyroxine. If your dog’s test result is lower than usual, he has hypothyroidism.

Some pets will have low TT4 levels and normal T4 levels by ED. These dogs don’t have hypothyroidism. Your dog may need additional tests to diagnose the problem depending on your pet’s condition.