Hyperparathyroidism in Dogs

Overview of Canine Hyperparathyroidism

Primary hyperparathyroidism is a disorder resulting from excessive secretion of parathyroid hormone (PTH) by one or more of the parathyroid glands located in the neck. The excessive amounts of PTH cause an elevated calcium level in the bloodstream, and this can have harmful effects on the body and can make dogs ill.

The most common cause of primary hyperparathyroidism is a single benign tumor, called an adenoma, on one of the parathyroid glands. Malignant tumors of the parathyroid gland are much less common.

Primary hyperparathyroidism is much more frequently diagnosed in dogs as compared to cats. Older dogs are more commonly affected (average age is 10 years). Males and females are equally affected. Keeshonds have a higher incidence than other breeds. A genetic marker associated with primary hyperparathyroidism has been found in the Keeshond.

Veterinarians can submit tests to determine the likelihood of disease in individual Keeshound dogs. The goal is for breeders to use test results to make breeding decisions and to eventually eliminate the disease from the breed. Test inquires can be submitted through the Cornell Animal Health Diagnostic Center. For more information, visit the lab’s Web site at www.vet.cornell.edu/faculty/Goldstein.

At first, the mildly elevated calcium levels don’t cause any symptoms. As time progresses and the calcium levels continue to rise, clinical symptoms appear. Three main body systems are usually affected: the gastrointestinal system, the kidneys, and the nervous system.

What to Watch For

Common symptoms of Hyperparathyroidism in Dogs may include:

• Excessive thirst and urination
• Listlessness
• Weakness or intolerance to exercise
• Poor appetite
• Shivering
• Loss of muscle mass
• Vomiting
• Constipation
• Stiff gait
• Difficult or abnormal urination, such as straining, bloody urine, increased frequency of urination

Diagnosis of Hyperparathyroidism in Dogs

• A complete medical history and physical examination
• Blood tests will be necessary to confirm the elevated calcium levels
• Urinalysis
• Ultrasound of the neck, as well as other affected organ systems
• X-rays
• An electrocardiogram to trace the electrical activity of the heart

Treatment of Hyperparathyroidism in Dogs

Treatments for primary hyperparathyroidism may include the following:

• Surgical removal of the abnormal parathyroid gland
• Hospital admission and administration of intravenous fluids and various medications may be necessary in cases where the calcium level in the bloodstream is dangerously high

Home Care and Prevention

Give medications as directed. If the abnormal parathyroid gland was surgically removed, dogs will occasionally develop signs of LOW calcium 1 to 7 days post-operatively. Carefully monitor your pet at home for signs of low calcium, including panting, nervousness, muscle twitching, leg cramping, stiff gait and seizures.

There is no known cause for primary hyperparathyroidism, therefore, there is no preventative care.

In-depth Information on Hyperparathyroidism in Dogs

Primary hyperparathyroidism is a glandular disorder in which excessive secretion of a hormone called PTH (parathyroid hormone) by one of the parathyroid glands located in the neck causes the calcium levels in the bloodstream to rise. The defect in the parathyroid gland is usually due to a solitary benign tumor in one of the glands. Occasionally, a malignant tumor of one of the parathyroid glands is responsible. Mild elevations of calcium usually cause no clinical symptoms; however, as calcium levels continue to rise, signs of illness develop.

Three body systems are most commonly affected: the gastrointestinal system, the kidneys, and the nervous system. There are many other disorders that can cause elevation in calcium levels. The diagnostic tests recommended will help differentiate hyperparathyroidism from the following:

• Cancer. Certain types of cancer can cause an elevation in serum calcium levels.
• Rat poison ingestion. There are certain types of rodenticides that work by raising the calcium level in the bloodstream.
• Addison’s disease. This is a disorder of the adrenal glands that frequently causes high serum calcium.
• Chronic kidney failure. Approximately 10 to 20 percent of pets with chronic kidney failure will have elevated calcium levels
• Fungal disease. A few fungal disorders have been reported to cause elevations in calcium levels. This is fairly uncommon
• Excessive supplementation of the diet with Vitamin D. Vitamin D will increase calcium levels in the blood. Too much vitamin D, given as a dietary supplement, can raise the calcium levels too high

Diagnosis In-depth

The following tests are commonly recommend to diagnose dogs with hyperparathyroidism:

• A complete medical history and physical examination should be performed.
• Routine blood tests will be necessary to confirm the elevated calcium levels, and to help monitor treatment.
• Special blood tests, such as measurement of the actual amount of PTH in the bloodstream, may be required for diagnosis. Measurement of the ionized calcium – the highly active, most important form of calcium – may also be necessary.
• Urinalysis may be needed in cases where difficult or abnormal urination is a major clinical sign.
• Ultrasound of the neck may identify a tumor in one of the parathyroid glands and confirm the diagnosis. If the kidneys or bladder are affected, ultrasound may also yield valuable information about these organs as well.
• X-rays may be necessary to rule out cancer as a cause for the high calcium levels in the blood.
• Lymph node and bone marrow evaluation may be necessary to rule out lymphosarcoma, a type of cancer that commonly causes elevated calcium levels.
• An electrocardiogram (EKG) may be useful if the high calcium levels are causing an abnormal heart rhythm.
• Surgical exploration of the neck to look for a parathyroid tumor is occasionally performed as a diagnostic tests when all other tests fail to yield a definite explanation for persistent elevations in calcium levels.

Treatment In-depth

• Surgical removal of the abnormal parathyroid gland is a relatively easy procedure that usually cures the condition. The parathyroid gland that is removed should be submitted to a pathologist to assess whether the tumor is benign (an adenoma) or malignant (a carcinoma).
• In cases where the calcium level is dangerously high, hospitalization and administration of intravenous fluids (saline) may be necessary to lower the calcium and stabilize the patient before considering surgery.
• A diuretic such as furosemide may be needed in addition to intravenous saline to enhance the excretion of calcium in the urine.
• Glucocorticoids may also be given to enhance urinary excretion of calcium.
• Calcitonin is a hormone that counteracts the effects of excessive parathyroid hormone (PTH), and helps lower the dangerously high calcium levels.
• Plicamycin is another drug that is occasionally used to lower high levels of calcium.
• Bicarbonate may be given, in conjunction with intravenous saline and diuretics, to shift the amount of ionized calcium (the dangerous form) to unionized calcium (a safer form).

Follow-up Care for Dogs with Hyperparathyroidism

Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your dog does not rapidly improve.

• Administer all prescribed medications as directed. Alert your veterinarian if you are experiencing problems treating your dog.
• Closely monitor your dogs during the critical one to seven day post-operative period for signs of low calcium such as panting, nervousness, muscle twitching, leg cramping, stiff gait or seizures.
• Return to your veterinarian for regular check-ups and blood tests to see that calcium levels are maintained in the normal range, as well as to monitor any damage that may have occurred to any other body systems, especially the kidneys.