Although it sounds somewhat similar to hyperthyroidism, hyperparathyroidism affects the body much differently. The parathyroid glands are located right next to the thyroid glands and work to balance the levels of calcium and phosphorus in the blood by secreting parathyroid hormone or PTH. This hormone will cause the absorption or release of calcium from the bones in the skeletal system to regulate the blood calcium and phosphorus levels. The Keeshond is the breed most commonly associated with primary hyperparathyroidism.
There are actually two different types of hyperparathyroidism caused by two very different sets of circumstances. The first type of hyperparathyroidism, called primary hyperparathyroidism is caused when the parathyroid glands become tumerous. Usually the tumor is benign and is known as an adenoma. This tumor causes the parathyroid to produce large amounts of PTH, resulting in highly elevated calcium levels in the blood. In most cases this tumor is found in older dogs between the ages of 7 to 12 years, with the average age of diagnosis being 10 years. Diagnosis is confirmed with blood tests and ultrasound of the neck area along with x-rays.
Symptoms of primary hyperparathyroidism include vomiting, excessive drinking and urination, lack of appetite, lack of energy, unwillingness to move or exercise, blood in the urine or straining to urinate. Since this may look like diabetes or other conditions, blood tests must be done to verify the levels of PTH and calcium in the blood. Treatment is surgical removal of the diseased parathyroid gland and close monitoring of blood calcium levels. Since many times the condition is very advanced before it is diagnosed there is often ongoing health problems for these dogs that are a result of the high calcium levels in the blood for prolonged periods of time.
In secondary hyperparathyroidism the cause is completely nutritional. Puppies or dogs that are fed all meat diets without appropriate bones or balance, high quality dry foods for calcium will develop elevated phosphorus levels and very low calcium levels in the blood. This will trigger the parathyroid to produce PTH, which will draw the calcium from the dog's body, resulting in leaching of calcium from the bones. The result is poor growth and development, weak joints and bones, painful movement, arthritis at a young age, fractures and breaks and malformation of the skeleton. In puppies, especially those of larger, heavier breeds the legs may become splayed and the gait severely altered through the malformation of the leg bones. The condition can be corrected by introducing a balanced premium kibble or food that has the correct calcium and phosphorus content or adding additional calcium to the diet in the form of bones and calcium rich supplements. It is important to note that the actual physical deformations or weaknesses cannot be corrected once it has developed so a balanced nutritional program is essential. Avoid feeding all meat diets, especially those high in organ meats, without lots of access to bones, calcium rich foods and supplements as prescribed by a vet.