Posted on April 23, 2017
Canine Primary Hyperparathyroidism
Hyperparathyroidism is a hormonal imbalance caused by excess (hyper) production of parathyroid hormone. This disease occurs in middle-aged and older dogs, males and females alike. Keeshonds appear to be genetically predisposed to hyperparathyroidism.
What is parathyroid hormone?
Parathyroid hormone (PTH) is produced within the parathyroid glands. Most dogs have four of them and they are pretty darned tiny, measuring in at two to four millimeters. They are located just beneath the skin surface of the neck adjacent to the thyroid glands.
PTH is responsible for maintaining normal levels of calcium and phosphorus levels within the body. It accomplishes this by regulating the amounts of calcium and phosphorus absorbed by the gastrointestinal tract, eliminated from the body by the kidneys, and released from bones into the blood stream. Too little parathyroid hormone (hypoparathyroidism) results in a blood calcium level that is too low and a phosphorus level that is too high. Too much parathyroid hormone (hyperparathyroidism) results in just the opposite- elevated calcium and decreased phosphorus.
Primary hyperparathyroidism is caused by a benign tumor within one or more of the parathyroid glands. Parathyroid tumors are functional meaning they produce excess PTH. The adjective “primary” is used when describing this form of the disease because the abnormality is within the gland itself.
Secondary hyperparathyroidism occurs when either kidney disease or a dietary deficiency triggers the parathyroid glands to produce excess PTH.
Many dogs with hyperparathyroidism appear completely normal. The disease is suspected when an elevated blood calcium level is picked up on routine blood screening. Symptoms associated with hyperparathyroidism are a result of increased calcium within the bloodstream. The most common symptoms associated with hyperparathyroidism include:
- Increased thirst
- Increased urination
- Decreased appetite
Some affected dogs develop calcium-laden bladder stones that can cause straining to urinate, increased frequency of urination, and blood within the urine.
Blood testing is the mainstay for figuring out whether or not a dog is hyperparathyroid. An increased ionized calcium level in conjunction with an increased or normal PTH level is consistent with the diagnosis of hyperparathyroidism. The diagnostic icing on the cake is identification of an enlarged parathyroid gland via ultrasound of the neck.
Surgical exploration of the neck to remove the enlarged parathyroid gland(s) is the most common treatment for hyperparathyroidism. The surgeon identifies and removes the enlarged gland(s).
A nonsurgical method of treatment is referred to as glandular ablation. Using ultrasound guidance, a small volume of ethanol is injected directly into the parathyroid gland destroying the tissue. Extreme care must be taken to prevent any of the ethanol from leaking out of the parathyroid gland capsule.
Following either form of treatment, the patient’s blood calcium level must be followed closely for a period of a several days to a few weeks. It’s not uncommon for the calcium level to plummet following surgery or gland ablation. This is because the remaining parathyroid glands have been “on vacation” as a result of the overachieving gland. They need a chance to wake up and ramp up PTH production.
It’s important to note that, over time, an elevated blood calcium level can cause kidney damage that is often irreversible. For this reason, it is important to treat in a timely fashion, even those dogs who are free of significant symptoms.
The outcome with treatment of primary hyperparathyroidism is excellent assuming that:
- A veterinarian with a high skill level is involved. For surgical treatment, it is ideal to employ a veterinary surgical specialist. A veterinarian who specializes in radiology or internal medicine is the best choice for performing ablation therapy.
- There is vigilant monitoring and treatment of fluctuating blood calcium levels following parathyroid gland surgery or ablation.
Have you ever had a dog with hyperparathyroidism? If so, how was your dog treated and what was the outcome?
Nancy Kay, DVM
Diplomate, American College of Veterinary Internal Medicine
Author of Speaking for Spot: Be the Advocate Your Dog Needs to Live a Happy, Healthy, Longer Life
Author of Your Dog’s Best Health: A Dozen Reasonable Things to Expect From Your Vet
Recipient, Leo K. Bustad Companion Animal Veterinarian of the Year Award
Recipient, American Animal Hospital Association Animal Welfare and Humane Ethics Award
Recipient, Dog Writers Association of America Award for Best Blog
Recipient, Eukanuba Canine Health Award
Recipient, AKC Club Publication Excellence Award
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Please visit http://www.speakingforspot.com to read excerpts from Speaking for Spot and Your Dog’s Best Health. There you will also find “Advocacy Aids”- helpful health forms you can download and use for your own dog, and a collection of published articles on advocating for your pet’s health. Speaking for Spot and Your Dog’s Best Health are available at http://www.speakingforspot.com, Amazon.com, local bookstores, and your favorite online book seller.