Hyperparathyroidism in Dogs
Key takeaways
Hyperparathyroidism in dogs refers to excessive release of parathyroid hormone from the parathyroid glands.
- Parathyroid hormone (PTH) is a major regulator of calcium levels in the bloodstream and responds to low blood calcium levels by increasing calcium release from the bones and absorption of calcium from food in the intestinal tract
- Disease affecting the parathyroid glands themselves, like tumors, or that reduce blood calcium levels, such as kidney failure, can result in excessive PTH production
- Symptoms include excessive urination, increased thirst, seizures, muscle tremors, and lethargy
- Diagnostics to identify the underlying cause include physical examination, bloodwork, and diagnostic imaging
- Treatment depends on the underlying cause but may include surgery, dietary changes, or medications to balance calcium levels
- The prognosis varies from excellent, in the case of dietary deficiencies, to poor, in the case of renal failure or malignant tumors
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A closer look: Hyperparathyroidism in Dogs
Hyperparathyroidism occurs when the parathyroid glands produce excessive amounts of parathyroid hormone (PTH), a hormone responsible for regulating calcium balance within the body. When calcium levels in the bloodstream are low, the parathyroid glands produce more PTH, which stimulates calcium release from the bones and encourages calcium absorption from the digestive tract.
Hyperparathyroidism is an uncommon condition in dogs, however it can be an indication of potentially life-threatening conditions such as cancer, nutritional deficiencies, or kidney failure. Dogs showing symptoms of hyperparathyroidism require prompt veterinary examination to determine the underlying cause and begin treatment.
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Risk factors
Depending on the severity of disease, excessive calcium release from the bones may make them fragile or rubbery. In many cases, the jaw is the most severely affected bone, causing “rubber jaw."
Possible causes
Hyperparathyroidism can arise due to disease in the parathyroid glands themselves (primary), or due to diseases that lower blood calcium levels (secondary). In response to increased PTH production, blood calcium levels rise rapidly, resulting in the symptoms of hyperparathyroidism.
Primary hyperparathyroidism is usually caused by a tumor within the parathyroid gland that produces excessive amounts of PTH, regardless of blood calcium levels. In some cases, genetics may play a role in the development of primary disease.
Secondary hyperparathyroidism is associated with dietary calcium deficiencies or kidney disease, which converts calcium into a form unusable by the tissues. The parathyroid gland responds to the resulting chronically low blood calcium levels with excessive PTH production.
Main symptoms
In some cases, dogs may show no symptoms of hyperparathyroidism.
Testing and diagnosis
Diagnosis of hyperparathyroidism first focuses on confirming elevated parathyroid hormone levels, then identifying the cause for the elevation. Diagnostic tests include:
- Physical examination
- Bloodwork, including measuring blood calcium and PTH levels
- Diagnostic imaging, including ultrasound
Further testing depends on the type of hyperparathyroidism suspected, and may include biopsy, nutritional evaluation, or surgical exploration.
Steps to Recovery
Treatment focuses on the underlying cause, and can vary widely. Treatment may include:
- Surgery
- Changes in the diet
- Medications to treat kidney failure
- Medications to slow release of calcium from the bones
- Medications to increase urination to remove excess calcium
- IV fluids
The prognosis of hyperparathyroidism depends on the underlying cause. Most dietary calcium deficiencies are rapidly treated by a diet change, and have a good prognosis. Dogs with primary hyperparathyroidism due to a parathyroid gland tumor typically have an excellent prognosis with appropriate surgical intervention, as long as the tumor is not malignant. Secondary hyperparathyroidism due to kidney failure has a guarded to poor prognosis, as kidney damage is generally irreversible by the time hyperparathyroidism develops. With appropriate treatment, the progressive of kidney failure can be slowed and symptoms may be reduced.
Prevention
Secondary hyperparathyroidism due to dietary imbalances can be prevented by feeding an age-appropriate, balanced diet that meets AAFCO standards. Other forms of hyperparathyroidism are difficult to prevent, but routine examination by a veterinarian may identify changes early leading to better outcomes.
Is Hyperparathyroidism in Dogs common?
Hyperparathyroidism is uncommon in dogs.
Typical Treatment
- Dietary changes
- Surgery
- Medications to treat kidney failure
- Medications to increase calcium excretion and decrease release
