Juvenile Hyperparathyroidism in Dogs

Juvenile hyperparathyroidism is not common in dogs but has been recently on the rise, probably because of better technology and testing procedures. The first noticeable signs of this disease may be mild and you may not even notice them at all. This is likely found by a blood test during a routine veterinary visit. Mineralization in the kidneys and lungs can be expected in dogs that have gone untreated. This can cause considerable damage that may be life-threatening if not treated right away. If your puppy is not growing at an expected rate or suddenly loses his appetite, you should visit your veterinarian right away for tests.

Juvenile hyperparathyroidism is a hereditary endocrine condition which usually affects German Shepherd and Keeshond breeds, although there have been cases in other breeds and older dogs. There are two types of hyperparathyroidism, which are primary and secondary. However, with juvenile hyperparathyroidism, it is considered to be primary.

There are several reasons for a dog to have hyperparathyroidism such as nutritional problems, a tumor on the parathyroid glands, a congenital abnormality, or renal problems, but juvenile hyperparathyroidism is the congenital type. All of these cause excess amounts of the parathyroid hormone (PTH) to be released and the symptoms are the same no matter which type of hyperparathyroidism your dog has. This condition causes abnormal amounts of calcium and phosphorous in the blood, which is what produces the symptoms of digestive upset and muscle atrophy.

Dogs with juvenile hyperparathyroidism can show a variety of symptoms depending on the progression of the disease and how many glands are affected. Too much calcium in the body affects many important bodily functions of the skeletal, nervous, renal, and digestive systems. Because PTH slowly causes the release of calcium from the bones, certain symptoms such as delayed growth are not noticed right away. Some of the most often reported symptoms are:

• Weakened muscles
• Decreased muscle mass
• Frequent urination
• Excessive thirst
• Stiffness
• Sleepiness
• Appetite loss
• Vomiting
• Constipation
• Stunted growth
• Mineralization of the lungs (breathing difficulty, coughing, wheezing)
• Mineralization of the kidneys (lack of urination, fluid retention, lethargy)

 Types

• Primary hyperparathyroidism is rare and is usually found as a congenital disorder or is caused by a tumor on the thyroid glands
• Secondary hyperparathyroidism may be caused by a long-term kidney problem, nutritional imbalance (too much or too little calcium), trauma, or an infection

This is an inherited autosomal recessive trait that affects a certain age, sex, and breed. Some of those most often reported include:

• Pups under six months of age
• Males
• German Shepherd
• Keeshond
• Jack Russell Terrier
• Chihuahua
• St. Bernard
• Miniature Schnauzer

A physical examination will be done on your dog first, paying special attention to the thyroid area (the neck). Vital signs, palpation and auscultation, and overall condition will be assessed as well. Blood tests are necessary to rule out diabetes, renal disease, inflammatory blood disease, or neoplastic disorders. Most often, the blood tests will show increased calcium, nitrogen, and phosphatase concentrations, a decrease of phosphorous in the blood, and a decrease of gravity in the urine. Also, x-rays may show growths on the parathyroid glands and reduced bone density anywhere in the body.

The excess calcium in the body causes the release of calcium from the bones, which makes the bones weak and creates a stunted growth. In addition, an electrocardiogram (ECG) is often performed to check the electrical activity in the heart because the imbalance of important nutrients can cause irregular heart functioning. The results will probably confirm prolonged QT intervals and a prolonged ST-segment. Other tests the veterinarian may perform include a CT scan, MRI, or ultrasound.

The treatments include surgery and medication. A surgical thyroidectomy or ablation are both common treatments that have few complications such as hypocalcemia.

Thyroidectomy

The veterinarian will make a midline incision in your dog’s neck and check both sides of the neck to see all four of the parathyroid glands. The affected glands will be removed and the others will remain as they are.

Ablation

This procedure is easier on your dog since it does not include opening up the neck. It is done by using a fine needle to inject ethanol into the tumors to destroy them.

Medication

This therapy is usually temporary or may be used in cases when your dog cannot handle surgery. Intravenous (IV) fluids given to induce urination to flush the kidneys may be beneficial. Corticosteroids (prednisolone or prednisone) may also be given to reduce the amount of calcium in the blood. However, steroids have been known to cause dangerous side effects such as infection, diabetes, and ulcers. Diuretics can help suppress the calcium levels but may also cause kidney damage.

The veterinarian will probably keep your dog for several days to monitor calcium levels because hypocalcemia is one of the most common complications after treatment. Once the veterinarian believes the levels are normalized, you will get to go home but you should make sure you keep an eye out for any complications.