Thyroid Problems in Dogs: Symptoms, Diagnosis And Treatment

Thyroid Problems in Dogs
Wyatt Robinson
Written by Wyatt Robinson

Thyroid disorders are considered as some of the most prevalent diseases affecting the canine family and continued to garner the interests of dog breeders and medical researchers. But despite the attention that the diseases have continued to garner over the years, together with the development and enhancements of more accurate diagnosis tests, detection of the disorders is still no easy work. This is mainly because, many times the symptoms are legion and sometimes they tend to be inconceivable.

Thyroid disorders attack the thyroid glands that are usually located in the neck region. In both humans and dogs, the thyroid glands handle the production of Thyroxine and Triiodothyronine hormones that handle regulating various processes in the dog and human body. The various processes that are controlled by the two hormones, Thyroxine, and Triiodothyronine include metabolism, regulation of body temperature, heart rate, breathing, weight and many others.

Weakened dog

Unknown for many people, thyroid problems are inheritable and can be passed from one dog to another within the same family line. This in turn means that if one dog shows symptoms or is diagnosed with any of the thyroid disorders, the chances are that the disease will be passed over to the next generation. The ability of the disease to pass from one generation to another is the main reason most breeders have shown a tremendous amount of interest in the diseases.

All in all, a slight change of any of these hormones will result in the development of diseases and disorders that will mainly target the endocrine system. Just like humans, dogs may overlook or hide their discomfort until the symptoms become uncontrollable.

Symptoms of thyroid problems in dogs: hyperthyroidism and hypothyroidism

Before discussing the various symptoms, diagnosis and treatment of Thyroid disorders it is very important to understand the different type of thyroid disorders that are common to the canine family. There are two main types of thyroid diseases that are common in dogs and many times this diseases may or may not come with the growth and development of cancerous cells. The two types of thyroid disorders include:

  1. Hyperthyroidism
  2. Hypothyroidism


Commonly known as Active Thyroid and Hyperthyreosis, Hyperthyroidism is a medical condition where the thyroid glands become overactive and produces the two hormones i.e. Thyroxine and Triiodothyronine excessively. When the thyroid gland becomes overactive or produces an excess amount of hormones, the various processes in the dog’s body will speed up. Hence, the dog will experience nervousness, rapid heartbeat anxiety, and excessive sweating.

Furthermore, the dog may also experience other problems such as weight loss issues, sleeping problems, leg tremors, and many others. However, there are certain dogs and dog breeds that once attacked by hyperthyroidism may show or atypical signs like loss of appetite, weakness, and depression. Such group of dogs/patients are commonly referred to as apathetic.

Signs of hyperthyroidism in dogs

All in all, Hyperthyroidism is very rare in dogs and if it occurs many at times it is due to the presence of carcinoma within the thyroid glands which in turn results in the secretion of two thyroid hormones, the triiodothyronine (T3) and tetraiodothyronine (T4). Other causes of hyperthyroidism in dogs may include certain types of medical prescriptions that were used to treat hypothyroidism that in turn leads to the overproduction of Thyroxine.

Diagnosis of hyperthyroidism in dogs

Diagnosis of hyperthyroidism can be made by relying on the palpation of the thyroid glands which often becomes enlarged after the infection has kicked in. Apart from the preliminary diagnosis other standard tests such as chemical blood profiling, urinalysis, and a complete blood count is conducted. Chemical profiling is a medical procedure that is used to determine the concentration of T4 in the blood serum.

Many times, an infected patient will have a high concentration of T4 its blood, and if the concentration of T4 hormones is above the required concentration, then the dog is diagnosed with Hyperthyroidism. However, during the early stages of the disorder, the concentration of T4 hormones within the blood serum will be within the expected level thus making the diagnosis of the disorder a little bit difficult.

Hence for dog owners whose dogs may show symptoms of the disorder but the test results showing otherwise will be required to return to the veterinarian after some time for further tests. All in all, your veterinarian is going to conduct a series of tests so as to determine whether the dog is infected and if so, what level the disorder has advanced. Other tests may include Thyroid Gland Scintigraphy, which is used to diagnose Hyperthyroidism and also determine the location of an irregular thyroid gland tissue, chest x-rays, and Thoracic radiography.

Treatment of hyperthyroidism

Hyperthyroidism in dogs can be successful treatment by the use of antithyroid medications whose main function is to interfere with the secretion of thyroid hormones. If the dog has developed cancerous cells in the thyroid glands, or if the thyroid glands are larger than the expected size, then surgery can be used to remove the entire gland or part of the gland. After the surgery has been successful, the dog is supposed to be given a daily prescription of synthetic thyroid hormones so as to regulate the dog’s metabolism.

Another type of treatment that can be used to treat hyperthyroidism include the use of radioactive iodine that is usually injected into the dog’s thyroid glands. The main function of the radioactive iodine is to kill any cancerous cells that may be present in the thyroid glands. All in all, treatment for hyperthyroidism may vary depending on the dog’s state of health and age and also some treatments are not suited for certain dogs.

Radioactive iodine for dog

Apart from the use of conventional drugs in the treatment of hyperthyroidism, homeopathic treatment has also been effective in the treatment of the various symptoms of the disorder such as agitation and restlessness. Herbal medicine such as bungle weed, valerian, and lemon grass is used in the treatment of stress while also inhibiting the activity of the thyroid glands.


Unlike hyperthyroidism that is slightly rare in dogs, Hypothyroidism is a very common medical disorder and is usually as a result in the lowered release and production of T3 and T4 hormones. Also, it is very prevalent in large sized and medium sized dogs though the predisposition usually varies from one dog to the other. All in all, there are certain breeds that stand a higher chance of contracting hypothyroidism, they include;

  1. Irish Setters
  2. Doberman Pinschers
  3. Miniature Schnauzers
  4. Poodles
  5. Golden Retrievers
  6. Cocker Spaniels
  7. Great Danes

Furthermore, this disorder is also very common in middle-aged dogs especially those that are between 4 and ten years of age. It has also been scientifically proven that spayed females and neutered male dogs stand a higher chance of contracting the disease. There are several ways in which a dog can contract or develop hypothyroidism.

Hypothyroidism is an immune disorder that is also known as autoimmune thyroiditis meaning that the dog’s thyroid tissues are being attacked by the body’s immune system. While responding to the attack, the gland will first try and compensate the deficiency by producing higher amounts of the hormones.

Hypothyroidism in dogs

But after sometimes, the amount of hormones in the thyroid gland becomes depleted. This is usually the point where the dog begins to develop the various symptoms of the disease, hence leading to diagnosis. Another way that a dog can develop the disorder is if the dog’s Thyroxine production is unable to meet the amount or levels required by the body for metabolism and other processes.

Symptoms and diagnosis of hypothyroidism

Once a dog contracts Hypothyroidism, there are several symptoms that the dog may display with some of them being specific while the others being non-specific. Currently, there is no specific symptom that can be used to diagnose fully hypothyroidism.

However, there are several symptoms when combined can play a crucial role in the diagnosis of the disease. When diagnosing the disease, the veterinary officer will begin first by conducting a physical examination while at the same time taking the dog’s historical background into account. Furthermore, the veterinary may ask the dog owner a series of the question so as to determine what might have led to the development of the disease.


Establishing the exact cause of the disorder will require a series of thorough medical examination and analysis. A routine laboratory test that will include, a biochemistry profile, urinalysis and blood count, all of which will be conducted to determine as to whether the dog has developed hypothyroidism. By relying on the test results of the routine laboratory test, the doctor will be able to make an initial diagnosis.

However, the veterinarian officer is also required to conduct endocrine testing so as to diagnose fully and treat the condition. During endocrine testing, the levels of the two hormones, T3, and T4 in the blood serum will be measured and compared against the accepted levels. Once the levels are found, to be below the required amount, the veterinary officer will commence with the appropriate treatment.

In some cases, the doctor may conduct a radio graphic study so as to check for any abnormalities that may have led to the development of the condition or the dysfunction of the glands.

Treatment of hypothyroidism

Since hypothyroidism occurs when the hormones are below the required level, treatment is usually administered by replacing the missing hormones with synthetic ones. In cases where the condition is very serious thus necessitating the removal of the glands, the synthetic supplements will be used to replace the hormones that the dog’s body will no longer be able to produce.

One such medication is Levothyroxine, which is not only affordable but is also available in both tablet and liquid forms. Levothyroxine, Synthroid must be taken orally and on a daily basis or according to the instructions given by the veterinary officer. Before administering the medication, always ensure that the pet is on an empty stomach so that the drug can be adequately absorbed into his or her body. Furthermore for effective results, you can also choose to split the dosage, one in the morning, and the other in the afternoon.

After using the drug for one or two weeks, you will begin to notice that the dog may start to become hyperactive or alert. Apart from the use of a conventional form of treatments, it has also been found that certain dogs may benefit from using homeopathic remedies. Homeopathic remedies for Hypothyroidism include seaweeds and kelp since they contain high traces of iodine.

Also, you can also fennel, Alfalfa, Oats, Parsley and many others as remedies. However, it is very important to note that homeopathic remedies must be used under the guidance of a veterinary officer or your favorite homeopath so as to avoid overdosage of iodine.

Other types of thyroid disorders in dogs

Thyroid Gland Adenocarcinoma (Thyroid tumors)

Adenocarcinoma also referred to as thyroid tumor is a malignant form of cancer that has its origin in the thyroid glands and can metastasize to other organs and tissues within the dog’s body. Since iodine is an essential for the normal functioning of the thyroid glands, Adenocarcinoma has been found to be prevalent in areas where iodine is deficient.

Despite the factor that any dog breed can develop this disorder, it has been found that thyroid gland adenocarcinoma is more prevalent in certain dog breeds than others. Such dog breeds include golden retrievers, boxers, beagles and many others. Like any other carcinoma, thyroid tumors are very common in older dogs when compared to younger dogs.

Thyroid tumors

Since Adenocarcinoma is a malignant type of cancer, it has been found to spread to other areas such as the windpipe, esophagus, blood vessels, lungs and many others. During diagnosis, about 40-50 percent of the infected dogs will have visible signs of the tumor on other body parts. Furthermore up to 60 percent of the infected breeds are going to have the tumor affect both thyroid glands at the same time. Finally, about 10 percent of all the cases reported are going to have the tumor lead to the excessive production of the hormones.

Signs, symptoms, and diagnosis

The most common sign of Thyroid Gland Adenocarcinoma is the presence of mass protrusions (movable mass) or tumors on the pet’s neck region, especially where the thyroid glands are located. Since the tumor can affect and interfere with the nerves surrounding the voice box, there will be major changes in the tone or way the dog barks and also harsh breathing may also be noted.

In case the muscles and nerves controlling swallowing are also affected in the process, the dog may experience difficulty in swallowing. All in all here is a breakdown of the most common symptoms that are associated with Adenocarcinoma.

  1. Large Protrusions around the neck region
  2. Dyspnea-breathing problems
  3. Dysphonia (hoarseness in the voice)
  4. Weight loss
  5. Polyuria (an increase in the frequency/amount of urine passing)
  6. Polydipsia (an increase in thirst)

During diagnosis, the veterinary officer will conduct an exhaustive physical examination on the dog together with a urinalysis, biochemistry profiling and finally an analysis of the blood sample. Apart from the physical examination, the doctor may also require the dog owner to give an exhaustive history of the pet together with the onset of the symptoms. All in all, the most important test will be the determination of the hormonal level in the blood since an increase of Thyroxine has been noted in all patients with thyroid tumors.

Dog at vet checking Thyroid

During the test, the levels of TSH (Thyroid Stimulating Hormone) will also be established. The TSH is a hormone that is usually secreted by the dog’s brain and handles controlling the amount of T4 in the blood. Depending on the amount or level of the tumor, the veterinary officer may also decide to use other diagnostic tools such as Ultrasound Imaging, X-Rays, MRI (Magnetic Resonance Imaging and CT (Computed Tomography). Furthermore, the vet may also decide to conduct a biopsy on the infected tissue so that he or she can be able to establish as to whether the malignant cells are present or not.


According to estimates, about 25 to 50 percent of all infected patients will undergo surgery meaning a high majority of the cases may be treated without surgery. It is very important to note that tumors that are attached to the tissue below the neck are not to be removed at any cost. During surgery, the veterinary surgeon will begin the process, by making very precise incisions on the lower side of the pet’s neck thus separating the muscles that separate the gland and conclude by removing the tumor.

If the tumor has started to spread in the underlying tissues, the veterinary surgeon will use radiation therapy to stop the invasive cells from spreading any further. Radiation therapy is supposed to be administered on Mondays all the way to Fridays for a total of 18-21 days.

Dog scan

However, it has been proven that Thyroid tumors are somehow unresponsive to chemotherapy though when used in modality it can achieve some positive results. It is very important to note that chemotherapy treatment in dogs does not lead to hair loss.

Hence, hair loss should not be an issue of concern though vomiting and loss of appetite are some of the few side effects of chemotherapy in dogs. The use of radioactive iodine is also another form of treatment that is used to treat several types of thyroid tumors though high amounts of radioactive iodine may be required to treat the tumor effectively.

About the author
Wyatt Robinson
Wyatt Robinson

Wyatt Robinson had a great 25-years career as a veterinarian in United Kingdom. He used to be a member of British Veterinary Association and worked in 3 pet hospitals in London and Manchester. He is shining when he sees his pets healthy and full of energy and it is his duty to help other dog owners to keep their best friends full of life.