How primary hyperparathyroidism affects dogs

Hyperparathyroidism is a condition that affects the parathyroid glands-four small glands located alongside of the thyroid gland itself, and which are responsible for producing and moderating certain types of hormones. The hormones that these glands produce regulate the levels of phosphorus and calcium in the blood, by absorbing calcium from the bones and passing it back into the bloodstream.

When the parathyroid glands become overactive for any reason, this is known as hyperparathyroidism, in contrast with hypoparathyroidism, or underactive parathyroid glands.

Hyperparathyroidism comes in two different forms-primary and secondary. Primary hyperparathyroidism occurs when a tumour develops on one (or more) of the parathyroid glands and causes an increase in the calcium level of the blood-called hypercalcaemia-or because the dog has a congenital defect that affects the parathyroid glands.

Secondary hyperparathyroidism can be caused as a secondary effect or complication of other health conditions, such as vitamin deficiencies or kidney disorders.

Why any given dog might develop a tumour on their parathyroid glands and suffer from primary hyperparathyroidism is not fully understood-but the condition does seem to appear more commonly in certain breeds of dogs than others, which indicates that there may be a hereditary element to the condition.

In this article we will look at hyperparathyroidism in dogs in more detail, including how primary hyperparathyroidism affects dogs, and which breeds have the highest risk factors. Read on to learn more.

More about primary hyperparathyroidism in dogs

The parathyroid glands are four small glands located alongside of the thyroid gland, which is in turn located in the dog’s neck. If a tumour develops on one of these four glands, it can have a significant impact on the dog’s hormone levels and ability to regulate their parathyroid hormones, which can lead to a range of internal problems in the dog that can be hard to spot and diagnose.

The tumour need not necessarily be malignant, either-even a benign rumour will impact on the glands’ ability to perform normally. Primary hyperparathyroidism is most commonly associated with tumour formation, but certain congenital health conditions that affect the parathyroid glands can also cause primary hyperparathyroidism too.

What sort of dogs are at risk of the condition?

Any dog has the potential to develop a tumour on one of the parathyroid glands, or to be born with a congenital defect or health condition that may affect the parathyroid glands. Why either of these things might occur is not fully understood, but primary hyperparathyroidism is more common in a couple of dog breeds than it is in any others, which indicates that there may be a hereditary element in play.

The Keeshond is the breed most widely associated with primary hyperparathyroidism, but the German shepherd also seems to present with the condition slightly more than other breeds too. Both male and female dogs seem to have equal chances of being affected by the condition, and it does not appear to be more prevalent in unneutered dogs than neutered dogs.

The age at which the condition is first diagnosed or a tumour first found can be highly variable, but diagnosis is very uncommon in dogs under the age of around five. The condition is more common in senior and elderly dogs of around the age of ten than younger dogs, but the age of onset can be very variable.

What are the symptoms of primary hyperparathyroidism in dogs?

One of the main problems that arise when it comes to identifying a problem and getting a formal diagnosis of primary hyperparathyroidism is that dogs with the condition do not usually appear to be unwell or display any obvious symptoms, and the symptoms that do appear can be very subtle and easy to miss.

It is the higher than usual calcium levels in the blood that produce the symptoms that do appear, and in order to make a formal diagnosis, your vet will run a range of tests including blood panels, and if elevated calcium levels are found, this will help to direct the course of the diagnosis.

Some of the subtle symptoms of primary hyperparathyroidism you might notice in your dog at home are:

• Slightly higher levels of thirst and need to urinate.
• Weakness or lethargy.
• The development of urinary tract stones, due to the calcium deposits that build up.
• You may be able to feel a slight swelling in your dog’s neck if the parathyroid glands become enlarged.
• In severe long-term cases, affected dogs may fall into a coma.

Can the condition be treated?

Once your vet has formally diagnosed the condition, they will probably consider surgery to remove the tumour on the parathyroid glands, and in some cases if your vet is not totally sure on their diagnosis but all of the signs point to a potential tumour, they may perform an exploratory operation on the parathyroid glands.

The intention of this is to find out if there is a tumour present, and if so, to remove it. Providing that the tumour can be removed successfully, the hormone levels produced by the parathyroid glands should return to normal parameters, and correct the condition.