Low Production of Parathyroid Hormone in Dogs

Hypoparathyroidism in Dogs

Hypoparathyroidism is characterized by an absolute or relative deficiency of parathyroid hormone in the blood. The parathyroid hormone regulates calcium and phosphorus levels in the blood, normally increasing blood calcium levels by causing calcium to be reabsorbed from the bone. Low levels of parathyroid hormone secretion will therefore lead to low levels of calcium in the blood, a condition called hypocalcemia.

The parathyroid glands are small, hormone-secreting glands that are located on or near the thyroid glands, which are in turn located at the front of the neck, in alignment with the larynx and trachea.

In dogs, there is a predilection for hypoparathyroidism in toy poodles, miniature schnauzers, German shepherd dogs, Labrador retrievers, and terrier breeds. The average age of diagnosis is 4.8 years, with a range of six weeks to 13 years. There also appears to be a gender difference, as females tend to be diagnosed in higher numbers.

Symptoms

• Seizures
• Tense abdomen
• Wobbly, incoordinated, or drunken appearing movement (ataxia)
• Stiff gait
• Fever
• Facial rubbing
• Muscle trembling, twitching, or involuntary contractions of muscles
• Growling
• Panting
• Cataracts
• Weakness
• Increased urination and increased thirst
• Vomiting
• Lack of appetite

Causes

Hypoparathyroidism is most commonly of unknown cause, or is the result of an immune-mediated inflammation of the parathyroid gland.

Diagnosis

Your veterinarian will perform a thorough physical exam on your dog, taking into account the background history of symptoms that you are able to provide. Standard testing, including a complete blood profile will be conducted, as well as a chemical blood profile, a complete blood count, a urinalysis and an electrolyte panel. The results of these tests will usually return normal in the case of hypoparathyroidism, however, they are important in discounting any other underlying disorders.

Because there are several possible causes for the symptoms described here, your veterinarian will most likely use differential diagnosis. This process is guided by deeper inspection of the apparent outward symptoms, ruling out each of the more common causes until the correct disorder is settled upon and can be treated appropriately. The main problems associated with hypoparathyroidism that must be differentiated from other disease processes are seizures, weakness, muscle trembling, and twitching.

Some of the causes that will need to be ruled out are heart related diseases, metabolic diseases, such as hypoglycemia (low blood sugar) or hepatoencephalopathy (liver disease that affects the brain’s functioning). Neurological causes that will need to be ruled out are inflammatory diseases, tumors, or epilepsy.

An exploration of the cervical section of the throat may reveal that the parathyroid glands are absent or have atrophied (wasted).