Last Updated: 07/05/2025
Has your dog been diagnosed with an underactive thyroid? Read through our Vet-guide to learn about the causes symptoms and treatment of this disease.
Author: Dr Carla Paszkowski BVSc (Hons)
Reading Time: 35 minutes - long read
Has your dog been diagnosed with Hypothyroidism? Or perhaps you are a prospective puppy owner researching your favourite dog breed, but have discovered they are a breed prone to developing Hypothyroidism and want to prepare yourself? This guide should provide you with everything you need to know about Hypothyroidism in dogs.
2. Which dog breeds are prone to Hypothyroidism?
4. Diagnosis of Hypothyroidism
5. Treatment of Hypothyroidism
Source: VCA Hospitals
Hypothyroidism is a condition in which the thyroid gland (a small gland with two lobes that sit around the trachea in the throat) is underactive in the dog's body. The thyroid gland normally produces thyroxine (T4) and triiodothyronine (T3), which are hormones that help regulate the body's metabolism. If the dog suffers from hypothyroidism these thyroid hormones are reduced or absent, which leads to problems with the skin, coat, energy levels, heat regulation, and immune system.
Hypothyroidism is caused by disease or destruction of the tissue in the thyroid gland. The two most common processes that cause gland destruction are inflammatory and degenerative, as outlined below. These two causes make up approximately 95% of cases. Tumours of the thyroid gland are a rarer cause and may account for up to 5% of cases.
- 1. Inflammatory destruction - lymphocytic thyroiditis. This is the most common cause and is thought to be immune-mediated. In this type of disease, the immune system attacks its own thyroid gland.
- 2. Degeneration - idiopathic thyroid gland atrophy. This type of Hypothyroidism occurs when normal thyroid tissue is replaced by fat tissue. This root cause of this condition is poorly understood.
- 3. Tumours of the thyroid gland. Thyroid tumours are rare but can cause hypothyroidism in up to 5% of dogs.
Did you know? Thyroid hormones are normally used by the body to regulate the metabolism, keep the body warm, fight infection, and maintain a healthy skin barrier. When thyroid hormones are not being produced properly, these body systems are disrupted and cannot function abnormally.
Hypothyroidism usually occurs in middle-aged dogs (aged 4-10) of medium to large sized dog breeds. Desexed dogs also have a higher risk. Particular breeds that are prone to developing hypothyroidism include:
⢠Retrievers including Golden Retrievers and Labradors
⢠Dobermanns
⢠Dachshunds
⢠Boxers
⢠Cocker Spaniels
⢠Irish Setters
Puffiness of the face forming the classic 'tragic face' of hypothyroidism. Photo by Dr. Carol Foil, sourced from VIN Veterinary Partner.
Hypothyroidism usually occurs in middle aged and senior dogs. Symptoms typically appear gradually over an extended period of time.
Clinical signs of Hypothyroidism include:
Weight gain, often without an increase in appetite
Puffy skin, known as the classic 'tragic' face
Brittle or thinning fur, particularly over the torso, abdomen and tail
Reduced energy, lethargy and listlessness
Inability to stay warm - owners often notice their dog shivers or seeks heat more than they used to
Chronic skin and ear infections
Increased pigmentation of the skin
Inability to grow hair back after shaving (shaving alopecia)
There are other less common, signs of hypothyroidism that occur occsionally. These include reproductive problems, nervous systems abnormalities such as nerve pain or dragging the hind legs, eye issues such as dry eye, and thickening of the facial skin which creates a droopy look.
Diagnosis of Hypothyroidism requires a veterinary examination and blood tests. Your vet will need to complete a full physical examination, and rule out any skin infections with a skin scrape and cytology test.
Your vet will likely run the following tests:
- Baseline bloodwork (CBC / biochemistry)
- Urinalysis
- Total thyroxine level - also known as Total T4 or TT4. This test measures your dog's main thyroid hormone level. If it is low, this can be suggestive of a diagnosis - however total thyroid hormone can also be low from other disease processes that depress the immune system.
- Free T4 / TSH (thyroid stimulating hormone) levels. A full thyroid panel which measures TSH and free T4 is usually done after a low TT4 level was observed, as it is a more accurate indicator for hypothyroidism.
TSH (thyroid stimulating hormone) is produced by the pituitary gland to stimulate the thyroid to produce T4 and free T4. In a dog with hypothyroidism, Total T4 and Free T4 will be low, while TSH will be high or normal.
Photo credit: Hal Gatewood from unsplash
While hypothyroidism cannot be cured, the good news is that it can be easily treated with an oral medication. However, your dog will need to be treated with the oral hormone replacement for life.
The standard treatment for hypothyroidism in dogs is daily oral administration of levothyroxine. This drug is a synthetic version of thyroid hormone. Giving thyroid hormone daily helps replace the circulatory thyroid hormone concentrations and reverses the disease.
Did you know: treatment of hypothyroidism simply involves replacing the hormone that is low or absent, just like hormone replacement therapy in menopausal women.
Ongoing care with regular vet check ups will be necessary to monitor your dog's progress and response to medication.
In addition to giving your dog their medication daily, you will need to monitor your dog's skin and body weight to detect any changes. If the clinical signs disappear and your dog gets their appetite back, this is a good sign and means the medication is working. It's also important to feed your dog an appropriate food and limit treats and table scraps - read more about this below.
Unlike other conditions such as Kidney disease or Diabetes, a strict Prescription Diet is not required for Hypothyroidism. Most high quality adult diets - particularly those formulated for skin care - will meet the above criteria and keep your hypothyroid dog nourished and healthy.
Many dogs with hypothyroidism benefit from a skin care diet to help with any concurrent skin problems. Your vet may recommend a specific diet
As your dog begins to get their appetite and metabolism back with treatment, they may beg for treats and tidbits more. It is important not to give into the temptation to over treat them - and therefore limit treats, table scraps, and snacks, particularly those that are high in fat, salt, or sugar. Stick instead to healthy treats such as regular kibble, carrots, apples, or strawberries.
Diamond Care's Sensitive Skin Dry Dog Food is specially formulated with high-quality natural ingrediets, probiotics, and a grain-free formula with hydrolysed salmon as the single protein source. It is full of Omega-6 and Omega-3 fatty acids thanks to the salmon, flaxseed, and two separate oils, and completely grain free.
Major callouts: single protein, contains 5 beneficial bacteria strains as probiotics, grain and gluten free, and is one of the only foods on the market to use hydrolysed salmon instead of poultry.
Ingredients: Peas, pea flour, hydrolysed salmon, sunflower oil, flaxseed, natural salmon flavour, tomato pomace, salmon oil, dicalcium phosphate, calcium carbonate, DL-Methionine, choline chloride, taurine, dried Lactobacillus plantarum fermentation product, dried Bacillus subtilis fermentation product, dried Lactobacillus acidophilus fermentation product, dried Enterococcus faecium fermentation product, dried Bifidobacterium animalis fermentation product, vitamins and minerals.
Available in small, medium, and large breed varieties, this dry food is specifically formulated to soothe irritation and promote skin health in dogs prone to sensitive skin.
Major callouts: the inclusion of Omega 3 & 6 fatty acids for healthy skin, and a low allergen formula.
Ingredients: Rice, wheat gluten, wheat, animal fats, maize gluten, husked oats, maize, minerals, hydrolysed poultry liver, soya oil, beet pulp, fish oil (source of EPA and DHA), flax seeds (source of omega 3), fructo-oligo-saccharides, borage oil (source of gamma-linolenic acid), marigold extract (source of lutein)
Available in mini, small, medium, and large breed varieties, this dry food is formulated specifically for dogs with skin or digestive sensitivities, so may be ideal if your hypothyroid dog suffers from tummy troubles, too. It contains a gentle fibre blend to promote optimal nutrient absorption, easy digestion and healthy bowel function.
Major callouts: highly digestible, lean protein, antioxidants including Vit C and E.
Ingredients: Chicken, Chicken Meal, Yellow Peas, Cracked Pearled Barley, Brown Rice, Brewers Rice, Whole Grain Sorghum, Egg Product, Chicken Fat, Soybean Oil, Dried Beet Pulp, Chicken Liver Flavor, Lactic Acid, Flaxseed, Pork Liver Flavour, Potassium Chloride, Iodized Salt, vitamins & minerals
This Australian-made dry food is designed for dogs with sensitive skin and intolerances towards poultry.
Major callouts: grain and poultry free, uses mackerel meal as a primary protein and source of natural fish oil, and contains prebiotics, probiotics and superfoods including broccoli, blueberries and kelp.
Ingredients: Mackerel Meal, Tapioca, Field Peas, Chickpeas, Canola Oil, Vegetable Broth, Alfalfa, Vitamins & Minerals & Amino Acids, Fish Oil, Flaxseed, Sea Salt, Yucca Schidigera Extract, Chicory Root (Natural Prebiotic), Glucosamine, Tomato, Sweet Potato, Kelp, Carrot, Broccoli, Blueberries, Natural Antioxidants (including Rosemary Extract and Green Tea).
Please note: the above recommendations are general advice only. Your vet may recommend a Veterinary-Prescribed Dog Food if they feel that other health issues are present.
Supplements are generally not required if you are providing your dog with a balanced adult diet from a vet-recommended brand (like one of the diets recommended above!). However, hypothyroidism can create dry skin and dull fur, which can benefit from a number of nutrients supplemented, including:
1. Fish oil / omega fatty acids can help improve dull fur or inflamed skin, and strengthen the skin barrier.
2. Vitamins A, C and E can also help strengthen the skin barrier and promote a stronger immune system.
3. Zinc has antiinflammatory effects - particularly on collagen production, fatty acid metabolism and wound healing.
After more information about taking care of your dog with arthritis? Check out our video and additional articles below:
Arthritis in dogs: what causes it and how do I know if my dog is affected?
Obesity in pets: why it's a problem and what to do about it
