Hypothyroidism is a disease of the endocrine system; it is one of the most common endocrine disorders diagnosed in dogs. The endocrine glands secrete hormones necessary for regulating and maintaining metabolism, hair growth, muscle strength and many other bodily functions. The hormone imbalance created by an underactive thyroid can result in a cascading effect of other endocrine system disorders (i.e., diabetes, Cushing’s disease) as well as neurological problems. This blog explains the probable link between hypothyroidism, autoimmune thyroiditis, and GOLPP (also known as Geriatric Onset Laryngeal Paralysis and Polyneuropathy), and provides information on proper diagnostic testing and treatment.
What is Autoimmune Thyroiditis?
Autoimmune Thyroiditis or lymphocytic thyroiditis is a type of hypothyroidism. It is a disease of the thyroid gland caused by the dog's own immune system affecting the production of thyroid hormones which regulate metabolism in the body. In essence, the dog’s immune system attacks the thyroid gland. It is not fatal, but it can have some serious symptoms and there is no cure. Most cases of hypothyroidism occur in older dogs, and of those cases, a small percentage are attributed to autoimmune thyroiditis.
How is Autoimmune Thyroiditis Diagnosed and Treated?
Dogs with autoimmune thyroiditis develop autoantibodies against thyroglobulin, a protein that is involved in the synthesis of thyroid hormones called T4 and T3. The TgAA test is recommended for detecting this condition. This test, in conjunction with T3, T4, freeT4, AAT3, and AAT4 testing, will check levels of the various thyroid hormones and antibodies against the thyroid gland. Routine laboratory testing only checks T4 levels and is not an accurate test for diagnosing hypothyroidism or autoimmune thyroiditis. Left untreated, thyroid disease may lead to laryngeal paralysis.
Thyroid levels should be closely monitored during treatment. It is important not to under- or over-supplement thyroid hormones. The synthetic thyroid hormone levothyroxine is often used in treatment. Vitamin A, D, and E supplementation will support the immune system and endocrine function. Vitamin D levels should be tested before giving supplemental vitamin D. Kelp as a source of iodine will support thyroid function. Herbs such as Licorice root, Rehmannia, and Ashwaganda can help maintain hormonal balance. A detailed list of supplements and dosages for hypothyroidism can be found in my book “Keeping Your Pets Naturally Healthy.”
What is Laryngeal Paralysis and GOLPP?
Laryngeal paralysis is a condition in which the cartilages that protect the upper airway fail to open and close properly. There is nothing wrong with the cartilages themselves, but paralysis occurs due to the recurrent laryngeal nerve (RLN) and/or vagus nerve not sending a strong signal to the muscle. As a result, the muscle weakens and no longer opens the larynx effectively. Sometimes, one cartilage is involved, and in other circumstances, it is both.
Laryngeal paralysis can be congenital or acquired. Congenital laryngeal paralysis in dogs most often affects Huskies, Bouviers des Flanders, and Rottweilers. Acquired laryngeal paralysis is more commonly diagnosed. Breeds predisposed to this condition include Labrador Retrievers, German Shepherds, Golden Retrievers, Newfoundlands, Greyhounds, and Brittany Spaniels. A dog with autoimmune thyroiditis is at risk for developing laryngeal paralysis. However, treating autoimmune thyroiditis does not also treat laryngeal paralysis.
Symptoms of laryngeal paralysis include changes in the dog’s bark, high-pitched noisy breathing (stridor) which may worsen with exercise or excitement, coughing or gagging, especially when drinking or eating, difficulty inhaling fully, exercise intolerance, increased panting, and respiratory distress. In a dog with this disease, the obstruction of the airway makes cooling difficult and rapid overheating (heat stroke) can occur. Heat and humidity are brutal for dogs with this condition. If you observe any of these changes in your dog, see your veterinarian as soon as possible. Laryngeal paralysis in dogs is one of a handful of true veterinary emergencies.
GOLPP, Geriatric Onset Laryngeal Paralysis and Polyneuropathy, was recognized as a distinct disease in 2012 after research showed that many dogs with laryngeal paralysis have a generalized polyneuropathy (damage or disease of multiple nerves). The cause of GOLPP has not been discovered. Senior dogs with geriatric onset laryngeal paralysis polyneuropathy may have:
- Generalized weakness in all muscles, not just those in the upper airway.
- Trouble walking, unsteady gait, abnormal stance, or difficulty climbing stairs or getting up on furniture due to hind-end weakness.
- Gagging, difficulty swallowing, or regurgitation (process where undigested food is passively expelled through the mouth) due to esophageal dysfunction. Coughing or choking on water is also common.
- High risk of developing swelling of the laryngeal tissues.
How is GOLPP Diagnosed and Treated?
Tests used to diagnose GOLPP include:
- Blood work: CBC (complete blood count), serum chemistry and urinalysis will assess the status of many organs. Thyroid testing, including those mentioned earlier to diagnose Autoimmune Thyroiditis, will provide information on whether hypothyroid disease is present.
- A Laryngoscopy is performed using a short-acting anesthetic which allows evaluation of laryngeal movement during breathing.
- X-rays of the neck and chest will rule out other causes of paralysis such as cancer, trauma, or foreign body.
- An Esophagram evaluates esophageal function during swallowing using real-time X-ray (fluoroscopy).
- A neurological exam assesses gait, muscle tone, and awareness of leg position and reflexes.
- Electromyography (EMG) and nerve conduction testing while under anesthesia is performed to evaluate the condition of the muscles and peripheral nerves.
Supportive therapies for GOLPP include:
- Thyroid supplementation and support (as with hypothyroidism and autoimmune thyroiditis.)
- PEA and Omega 3 Fatty Acid supplementation helps to reduce nerve inflammation and repair nerve damage.
- Minimizing excitement/stressful situations and administering sedatives as needed to facilitate calmness.
- Avoiding hot, humid weather (i.e., cranking up the AC and staying inside during the hottest and most humid parts of the day).
- Using harnesses rather than neck leads and collars.
- Improve gait and stability – dogs with GOLPP may have trouble rising and stumble easily due to hind end weakness. Use nonslip rugs, yoga mats or toe grips to support gait.
- Bailey chair: One study estimated that two-thirds of dogs with GOLPP also have trouble drinking and eating as the disease progresses. A Bailey chair holds a dog upright while eating which makes the esophagus mostly vertical. This change in positioning takes advantage of gravity to help the food slide down the esophagus and into the stomach.
- Tie-back surgery: This procedure can be very successful but is not without its risk. The surgeon will approach the larynx through an incision on the dog’s neck. One of the cartilages will be “tied back” so that it is permanently open and not obstructing air flow. Dogs who have had this surgery are able to breathe better and are better able to lead normal lives. However, there is a 20% risk of dogs who undergo tie-back surgery to develop aspiration pneumonia. Aspiration pneumonia occurs when food or fluid is aspirated into the lungs, causing infection. Signs of aspiration pneumonia include lethargy, change in appetite, fever, nasal discharge, coughing and changes in respiratory rate or effort.
Studies show there is strong evidence for a causal relation between hypothyroidism and a variety of neurologic abnormalities including GOLPP; however, further studies are necessary to determine the full spectrum of disorders caused by hypothyroidism. The environment certainly plays a role in the uptick in endocrine disorders. The goal is to minimize exposure to chemicals considered endocrine disruptors. Ways to minimize environmental endocrine disruptors include decreasing or stopping vaccine usage and eliminating use of products containing polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs), dioxins, BPA (in plastics), phthalates (found in laundry detergents and cleaning products), herbicides (glyphosate is a known endocrine disruptor), and pesticides. As always, a healthy species-appropriate whole food diet that is minimally processed will go a long way to supporting your dog’s health.
While autoimmune thyroiditis, laryngeal paralysis, and GOLPP can be stressful diagnoses, there is hope. By knowing the signs, acting quickly, and partnering with your veterinarian, you’re ensuring the best possible outcome for your faithful companion. Changes in your dog’s behavior are always worth mentioning to your veterinarian, no matter how strange or insignificant they may seem.