Do you feel your furry fellow acting a little bit off? They might be gaining weight with the same diet plan, getting unusually tired, or losing a patch of fur. These could be signs of a thyroid condition common in dogs and humans alike—hypothyroidism. The good news is that after being diagnosed, the condition is well-controlled with medication.
This post is another in our series examining common co-occurring conditions with Cushing’s syndrome. In other posts, we have discussed diabetes, hypertension, and various skin conditions.
The Role of The Thyroid Gland
The thyroid gland is in the neck near the windpipe and is crucial in regulating a dog’s metabolism. It produces the hormones thyroxine (T4), triiodothyronine (T3), and a calcium-regulating hormone we don’t discuss in this post, calcitonin. T3 and T4 control various bodily functions, including heart rate, body temperature, and energy levels. These hormones ensure the body’s metabolic processes run smoothly in healthy animals. For example, the body uses thyroid hormones to maintain energy by influencing the synthesis, storage, and consumption of all three major macronutrient classes—lipids (fats), carbohydrates (especially glucose), and proteins. Thyroid hormones also control body temperature and affect heart rate. Moreover, they play an important role in maintaining healthy skin and coat while supporting normal growth and development.
As with the adrenal glands (which produce the hormones responsible for Cushing’s syndrome), the thyroid itself is regulated by a signaling hormone from the hypophysis (pituitary gland). However, a different pituitary hormone regulates the thyroid than the one that regulates the adrenal glands.
What is Hypothyroidism in Dogs?
Hypothyroidism is a condition that occurs due to the failure of the thyroid to produce enough T3 and/or T4 (or a failure outside of the thyroid to convert T4 into T3). With rare exceptions, as with Cushing’s, the problem creating the underproduction of thyroid hormones can either rest in a malfunctioning thyroid or in a malfunctioning hypophysis (pituitary), thus:
- The condition is described as “Primary” Hypothyroidism if the thyroid itself is the source of the problem. This usually is caused by a natural deterioration with age or by immune system attacks on the gland, but a tumor inside or adjacent to the thyroid could also lead to this condition.
- If the deficiency results from a problem in the hypophysis (pituitary gland), the condition is labelled “secondary” hypothyroidism. In this case, the hypophysis fails properly to signal that additional thyroid hormones should be produced, reducing the production of thyroid-stimulating hormones.
How To Tell If Your Dog Has Hypothyroidism?
Hypothyroidism is diagnosed in 0.2-0.8% of the overall dog population each year, with the incidence among Cushing’s dogs being higher. Here are some signs to watch for:
- Weight Gain: Despite no change in diet, dogs with hypothyroidism often gain weight due to a slower metabolism.
- Lethargy: Reduced energy levels and increased sleepiness are common. Dogs may seem less interested in playing or exercising.
- Hair Loss: Typically occurs on the trunk, tail, and around the face. The hair loss is often symmetrical and can be accompanied by a dull, brittle coat.
- Dry, Flaky Skin: The skin may become dry and flaky, leading to a dull coat. Some dogs may also develop thickened or darkened skin.
- Cold Intolerance: Dogs may seek out warm places and shiver more quickly, indicating they are less tolerant to cold temperatures.
- Recurrent Skin and Ear Infections: These can be persistent and difficult to treat, often due to the compromised skin barrier.
- Behavioral Changes: Dogs may appear depressed or mentally dull, showing less interest in their surroundings.
- Muscle Weakness: Generalized weakness and other neuromuscular problems can occur, making it difficult for dogs to move around comfortably.
- Bradycardia: A slower than normal heart rate can be observed in some dogs with hypothyroidism
Hypothyroidism Connection with Cushing’s Syndrome
Cushing’s syndrome, or hyperadrenocorticism, is another endocrine disorder. Cushing’s results from excessive production of cortisol and/or other hormones produced by the cortex of the adrenal glands. This condition can lead to or exacerbate hypothyroidism because cortisol, like the hormones released by the hypophysis, is also a regulator of thyroid activity, and, thus, high levels of cortisol suppress thyroid function. Dogs with Cushing’s syndrome often show similar symptoms to those with hypothyroidism, such as hair loss and lethargy, making it essential to differentiate between the two conditions for accurate diagnosis and treatment. If hypothyroidism is suspected, your veterinarian will likely order blood work to confirm levels of thyroid hormones, iodine and other markers to confirm or reject a hypothyroid diagnosis.
Prevention and Management
There are few ways to prevent hypothyroidism, but fortunately, it is usually easily managed with medication. Here are some ways that you can consider improving your dog’s health by countering hypothyroidism.
Regular Veterinary Check-Ups:
Early detection through routine blood tests can help manage the condition before it becomes severe.
Balanced Diet and Exercise:
Maintaining a healthy weight and regular exercise can support overall health and potentially reduce the risk of endocrine disorders. However, it is important to tailor the exercise regimen to your dog’s energy levels and physical capabilities.
In addition, some veterinarians recommend specific diets rich in nutrients like selenium and iodine, which support thyroid health. In some cases, supplements such as omega-3 fatty acids can help improve skin and coat conditions, which are often affected by hypothyroidism.
Monitoring for Symptoms:
Being vigilant about changes in your dog’s behavior, coat, and weight can help catch hypothyroidism early.
Treatment Options
The primary treatment for hypothyroidism is hormone replacement therapy. The most common medication is levothyroxine, a synthetic form of thyroxine (T4). This medication is typically administered orally and requires lifelong management. Regular blood tests are necessary to monitor hormone levels and adjust the dosage. With proper treatment, most dogs with hypothyroidism can lead everyday, healthy lives.
Conclusion
Cushing’s dogs are more susceptible than other dogs to hypothyroidism, so it’s crucial to be aware of the symptoms and seek veterinary care if you notice any signs. Early diagnosis and treatment can significantly improve your dog’s quality of life and help it live a long and healthy life.