Non-Inflammatory Myopathy of Endocrine Origin in Dogs

The endocrine system is comprised of the glands and the hormones those glands produce and secreted. Some familiar examples of hormones include insulin, thyroid hormone, and cortisol. It is known as the control center of the body, as the hormones produced are chemical messengers which travel all over the body to target areas. They “communicate” with these tissues or organs and “tell” them to increase activity or decrease activity.  These signals are controlled by the nervous system.

The endocrine system is in charge of controlling all of the body’s cells. It is in charge of many of the body’s processes, such as tissue function, growth, development, reproduction, and more. The human endocrine system is identical to those of canines and felines. The glands include the thyroid, pituitary, parathyroid, pancreas, ovaries, testes, and adrenal glands. 

Non-inflammatory myopathy is a disease of the muscles caused by an abnormality in the endocrine system. Non-inflammatory myopathy of endocrine origin in dogs is often the result of hypothyroidism and hyperthyroidism, or by the usage of corticosteroids. Hypothyroidism is when the dog’s thyroid does not produce enough hormone, and hyperthyroidism is when the dog has an overactive thyroid. Both can have significant and negative effects on the body.

Non-inflammatory myopathy in dogs is a muscular disease that is a result of the endocrine system not properly functioning. This disease is of hereditary origin.

Symptoms of non-inflammatory myopathy of the endocrine origin in dogs include:

• Weakness of muscles
• Deterioration of muscle mass
• Cramping
• Stiffness and achiness
• Struggling to swallow due to muscle weakness
• Vomiting or regurgitation

 Types

Types of conditions that can lead to myopathy of endocrine origin in dogs include:

• Auto-immune disorder
• Overactive thyroid
• Underactive thyroid

The types of conditions that cause myopathy of endocrine origin in dogs are hereditary. The gene is autosomal recessive, which means that two of the genes (one from each parent) are passed down to the dog.

In order to properly diagnose the dog’s condition as non-inflammatory myopathy of endocrine origin in dogs, the veterinarian will consider the differential diagnosis of specific conditions and rule them out, such as inflammatory myopathy. 

The veterinarian will perform a complete blood count, a biochemistry profile, and a urinalysis to examine the data for any signs of endocrine abnormalities. Included in the biochemistry profile is the serum creatine kinase test, to check for elevated activity.  Adrenal functioning tests and thyroid functioning tests will also be conducted.

The medical professional may also do imaging techniques, such as dynamic imaging studies to look at the pharynx and esophagus. This will check to see how the muscles are performing in terms of swallowing or any regurgitation. An electromyography, which tests muscle function, and a muscle biopsy may also be performed.

If your dog is diagnosed with non-inflammatory myopathy of endocrine origin, the treatment will be dependent upon the specific type. The dog may have myopathy as a result of steroid usage, hypothyroidism, or hyperthyroidism. 

Medication

For hypothyroidism, the veterinarian may recommend levothyroxine, which is a medication used to increase thyroid activity. Hyperthyroidism is usually the result of adenomas or cancerous tumors. Medications can include chemotherapy drugs such as doxorubicin or cisplatin.

Surgery

Surgery may be required if there is a tumor involved, such as a benign adenoma, to remove or partially remove the thyroid. Ablation of the thyroid may also be considered.

The dog will need to be monitored on a regular basis through blood work and other tests. In cases of severe myopathy, the veterinarian may suggest not breeding the dog, since this is an inherited disorder. With monitoring the dog, the prognosis is good with regular check-ups and watching for any symptoms and treating them as they arise. In some cases, the veterinarian will suggest keeping the dog stress-free, as stress may trigger the condition.