Hypothyroidism in Dogs: Causes, Symptoms, Diagnosis, and Treatment


Hypothyroidism is a prevalent endocrine disorder that affects dogs, disrupting the proper functioning of the thyroid gland. This condition leads to an inadequate production of thyroid hormones, resulting in a range of symptoms that can significantly impact a dog’s health and quality of life. This article aims to provide a comprehensive understanding of hypothyroidism in dogs, including its causes, symptoms, diagnosis, and available treatment options.

1. What is Hypothyroidism in Dogs?

Hypothyroidism is a hormonal disorder in dogs caused by the underproduction of thyroid hormones by the thyroid gland. These hormones are essential for regulating metabolism, growth, and overall cellular function in the body. When there is an insufficient level of thyroid hormones, the dog’s metabolism slows down, leading to a variety of symptoms and health issues.

2. Causes of Hypothyroidism

Hypothyroidism in dogs is most commonly caused by the gradual destruction of the thyroid gland’s tissue, leading to a decrease in hormone production. The primary cause of this destruction is often an autoimmune response, where the dog’s immune system mistakenly attacks its own thyroid tissue. Less commonly, certain medications, tumors, or congenital defects may contribute to the development of hypothyroidism.

3. Symptoms of Hypothyroidism

Recognizing the symptoms of hypothyroidism is crucial for early detection and appropriate management. Common signs of hypothyroidism in dogs include:

  • Weight Gain: Dogs with hypothyroidism often experience unexplained weight gain despite a decreased appetite.
  • Lethargy: Hypothyroid dogs may appear lethargic, lacking energy, and becoming less interested in activities.
  • Hair Loss and Dull Coat: A dog’s coat may become dry, brittle, and prone to excessive shedding.
  • Skin Problems: Hypothyroidism can cause skin issues, such as dryness, thickening, and darkening of the skin.
  • Intolerance to Cold: Dogs with hypothyroidism may become more sensitive to cold temperatures.
  • Muscle Weakness: A decrease in muscle mass and weakness in the limbs can be observed.
  • Changes in Behavior: Dogs with hypothyroidism may exhibit behavioral changes like irritability or depression.

4. Diagnosis of Hypothyroidism

If you suspect your dog has hypothyroidism or notice any of the mentioned symptoms, consult a veterinarian for a thorough evaluation. The diagnosis of hypothyroidism typically involves:

  • Medical History and Physical Examination: The vet will review the dog’s medical history and conduct a physical examination, assessing for any visible signs of hypothyroidism.
  • Blood Tests: Blood tests are crucial for measuring thyroid hormone levels and identifying abnormalities that indicate hypothyroidism.

5. Treatment Options

Once diagnosed, the treatment for hypothyroidism in dogs typically involves hormone replacement therapy. Synthetic thyroid hormones are administered orally to supplement the inadequate hormone production. Regular monitoring and adjustments to the medication may be necessary to ensure the dog’s thyroid levels are well-maintained.


Hypothyroidism is a common hormonal disorder in dogs that can significantly impact their well-being. Understanding the causes, symptoms, and available treatment options is essential for early detection and proper management. If you suspect your dog has hypothyroidism or notice any concerning signs, consult a qualified veterinarian for a thorough evaluation and personalized treatment plan to provide your beloved canine companion with the best possible care and support.