Whether you are a canine lover or a feline fan, you need to know that your pet is at risk of developing thyroid disorders – just like you. If your pet is looking or has been acting weird lately, then make sure to read on to learn more about the different thyroid issues that can affect your beloved pet.
Thyroid Disease in Dogs
Just like humans, dogs possess a thyroid gland – which is located along the neck. It is under the control of the master gland otherwise known as the pituitary gland.
Similarly, a dog’s thyroid gland produces thyroxine (T4) and tri-iodothyronine (T3), which regulates the body’s use of energy, as well as its response to other hormones. and other essential hormones.The thyroid gland releases calcitonin as well – a hormone essential for calcium control in the dog’s body.
If the aforementioned hormones are produced in either little or excessive amounts, the dog can suffer from a variety of metabolic problems. Examples include:
Similar to the human condition, hypothyroidism in dogs is marked by a slowed metabolism. It occurs due to the insufficient amount of hormones secreted by the thyroid gland.
Primary hypothyroidism in dogs, as stated in the case study of McKeown, is mostly caused by the destruction of the thyroid gland, as in the cases of idiopathic atrophy, lymphocytic thyroiditis, or neoplastic destruction. Secondary hypothyroidism, on the other hand, occurs due to the reduced secretion of Thyroid-Stimulating hormone by the pituitary gland.
The prevalence of hypothyroidism is much higher in the following:
- Middle-aged dogs of 4 to 10 years
- Medium to large-sized canines such as the Doberman Pinscher, Miniature Schnauzer, Cocker Spaniel, Dachshund, Airedale Terrier, Golden Retriever, and Irish Setter
- Neutered males and spayed female dogs
The common symptoms of hypothyroidism are the following:
- Dull and thin coat, flaky skin
- Hair thinning, hair loss, or increased shedding
- Obesity, weight gain sans appetite changes
- Exercise intolerance
- Muscle loss
- Cold intolerance
- Mental bluntness
- Reproductive changes
- Toenail and ear infections
- Possible seizures
- Possible heart and blood vessel disorders
Goiter, or thyroid enlargement, can manifest as a symptom of congenital hypothyroidism, especially in breeds such as that of the Toy Fox Terrier. This swelling, which commonly occurs in mammals, develops due to a low-iodine diet or one that is rich in goitrogens (food that affects thyroid functioning.) Due to the commercial diets of dogs, goiter development can be attributed to genetic problems or the side-effect of the antibiotic trimethoprim-sulfa.
A more serious thyroid condition which is common in the Golden Retriever, Beagle, Doberman Pinscher, and Akita is auto-immune thyroiditis. In this condition, the immune system destroys the thyroid gland, resulting in the primary symptom of Hypothyroidism . While it is a disease by itself, auto-immune thyroiditis can be a symptom of a graver malady, such as that of panendocrinopathy or systemic lupus erythematosus.
Hyperthyroidism symptoms in dogs can be quite similar to other conditions, which makes diagnosing a challenge for veterinary professionals. Since it is one of the most over-identified illnesses in dogs, veterinarians will base their findings not only on medical history and clinical symptoms, but on laboratory results as well.
Expect your vet to order for a T4 concentration blood test, which is done to gauge your dog’s thyroid levels. Other pertinent blood exams, such as that of T3 and TSH, might be requested by the vet as well.
A sub-normal level of T4, accompanied by the classical signs mentioned above, are the minimum requirements start hormone treatment with Levothyroxine or L-thyroxine. This synthetic drug is meant to make up for your dog’s low hormone levels.
The dosage will depend on your pet’s weight and thyroid levels, but it is usually taken daily for the remainder of your dog’s life. Results usually manifest in 1-2 months, with the vet making dosage adjustments as needed by the canine. Should the treatment fail, a possible underlying medical condition will be taken into consideration and a new form of treatment might be warranted.
Hyperthyroidism occurs when the thyroid gland secretes excessive amounts of hormones. As a result, your dog’s metabolism is set to overdrive. Symptoms of hyperthyroidism include:
- Increased appetite and thirst
- Vomiting and/or diarrhea
- Weight loss
- Increased excitability
- Excessive urination, increased amount of stool
- Thyroid gland enlargement
- Breathing difficulties (dyspnea)
- Heart problems such as murmurs, fast heart rate, enlarged heart (cardiomegaly), and congestive heart failure
The malignant condition called thyroid carcinoma is the primary reason why some dogs develop hyperthyroidism. This neoplastic growth is common in older dogs and in both sexes, however Golden Retrievers, Beagles, and Boxers seem to be at higher risk of developing the said condition.
Thyroid cancer proliferation can be quite rapid, with the study of Bezzola stating that it can easily invade nearby tissues, such as the esophagus, trachea, jugular vein, and larynx. As such, prognosis is dependent on the tumor size, cancer stage, and metastatic activity.
Apart from physical examination and a comprehensive medical history, lab exams such as complete blood count (CBC), blood chemistry, and urinalysis will be obtained by the physician. A working consideration for thyroid carcinoma might warrant fine needle aspiration biopsy as well.
Several options are available for dogs with hyperthyroidism due to cancer. The treatment of choice is the surgical removal of the tumor, which is known to prolong life expectancy. Another option is which is done in conjunction with surgery is radioactive iodine therapy, which works by controlling thyroid function and shrinking tumor size.
External beam radiation, on the other hand, is recommended for dogs with cancer that has metastasized to nearby structures. The treatment is delivered through a device such as a linear accelerator or a cobalt therapy machine.
Chemotherapy with the use of vincristine, cyclophosphamide, and doxorubicin can be done as well. According to the study of Mayer and MacDonald, this treatment is best for dogs with large inoperable tumors, or those with metastatic thyroid cancer.
Thyroid Disease in Cats
Similar to canines, felines have a thyroid gland which produces the hormones T3 and T4. Both are essential for the metabolic functions within a cat’s body.
As the most common gland condition in cats, hyperthyroidism is characterized by an increased amount of the hormone T4 in circulation. It can occur in any gender or breed, although it is more common in non-purebreds and older felines, usually manifesting at age 12 to 13.
Feline hyperthyroidism is usually caused by a thyroid adenoma, a benign mass that affects both thyroid glands. However, a study by Kohler et al contends that consumption of moist food and the use of aluminum tins can play pivotal roles in the development of the disease.
Hyperthyroidism symptoms can include:
- Weight loss despite a hearty appetite
- Messy appearance
- Increased thirst
- Excessive urination
- Increased shedding
Diagnosing hyperthyroidism in cats can be a bit tricky. After all, the symptoms mentioned above can also be seen in cats with inflammatory bowel disease, chronic kidney failure, diabetes, and intestinal cancer. To rule out these diseases, your vet will ask for a CBC, blood chemistry test, and urinalysis. Hyperthyroid cats usually demonstrate normal CBC and urinalysis results, although an elevation of liver enzymes will show up in the blood chemistry panel.
The best way to make a definitive diagnosis is with a T4 test, so as to check the levels of thyroid hormone in your cat’s bloodstream. While an elevation is expected in afflicted felines, 2 to 10% of cats will showcase normal T4 results – if they only have a mild case of hyperthyroidism.
Unfortunately, other diseases, which are common in older cats, can lead to normal T4 levels – another factor that can lead to a probable misdiagnosis of hyperthyroidism.
Despite the complicated nature of diagnosing hyperthyroidism, treatment options abound once the disease has been confirmed. Examples include:
- Anti-thyroid Medications. The gold standard when it comes to medication therapy is the use of Methimazole, also known as Tapazole. Positive results show after a mere 2 to 3 weeks. Although it is very effective, it comes with a variety of side effects such as appetite loss, lethargy, head and face itch, yellowing (jaundice), vomiting, and blood disorders. This lifetime treatment includes periodic CBC and T4 examinations to check the hormone levels in the bloodstream.
- Surgery. For hyperthyroidism caused by thyroid adenoma, a surgical intervention is usually required. Removal can be done easily, although anesthesia can pose a risk on older cats with pre-existing diseases. Compared to a lifetime of Methimazole treatment, it is deemed more economical in the long run.
- Radiotherapy. Another option for hyperthyroid cats with thyroid adenoma is treatment with radioactive iodine. Given intravenously, it travels to the thyroid gland where it destroys the afflicted tissues. While costly, one dose of radioactive iodine is enough to curb hyperthyroidism. The only downside is the prolonged hospitalization associated with radiotherapy. The confinement period is usually from 10 to 14 days. This is to ensure the safe levels of radioactivity in the cat’s urine or feces.
Hypothyroidism, also known as thyroid hormone deficiency, rarely occurs in cats. When it does, it happens more in kittens rather than adult cats. Hypothyroidism in cats is usually due to congenital disease, iodine deficiency, thyroid hormone overdose, surgery, or radioactive iodine therapy. As expected, its symptoms are the reverse of hyperthyroidism, and they include:
- Decreased activity and weakness
- Mental dullness
- Low body temperature
- Weight gain
- Unkempt look
- Hair matting and hair loss
- Delayed teething
An accurate medical history and physical examination are just some of the vital factors that can lead to an accurate diagnosis of hypothyroidism. It is highly important to determine which causes the condition, and such can be established with the help of a CBC, chemistry exam, and urinalysis. T3 and T4 testing will be ordered by a vet, as well as a radiographic exam to check the abnormalities that could lead to thyroid dysfunction. The expected results in hypothyroid cats are low T4 levels and elevated TSH levels.
Hypothyroidism is short-lived in cats, which is why treatment is barely recommended by vets. However, if it is deemed necessary, hormone therapy is appropriated for the duration of the cat’s lifetime. Adjustments are done every so often, depending on the feline’s recovery.
To answer the titular question above, the answer is yes – pets can have thyroid issues as well. Hypothyroidism is more common in dogs, while hyperthyroidism is more prevalent in cats. Age and breed can help dictate a pet’s predisposition to thyroid disease.
Diagnosing thyroid disorders is a challenge for veterinary professionals, and as an owner, an accurate description of your pet’s medical history can help lead to an accurate, definitive diagnosis.
Although such is the case, do know that thyroid disorders are treatable – and underlying malignancies can be addressed with early diagnosis and cure. With that being said, as an owner you have a great responsibility to have your pet checked should any of the symptoms above arise.