What Is Hyperparathyroidism?
The parathyroid glands are four tiny glands in the neck, next to the thyroid. They make parathyroid hormone (PTH), which controls how much calcium is in the blood. Hyperparathyroidism means these glands make too much PTH. This is different from hyperthyroidism, which involves the thyroid gland itself.
Types
- Primary: usually a benign growth on one parathyroid gland makes excess hormone, causing high blood calcium. It is seen mostly in older dogs, with Keeshonden at higher risk.
- Renal secondary: long-term kidney disease disturbs calcium and phosphorus, and the glands overwork to compensate. Common in cats with kidney disease.
- Nutritional secondary: a diet too low in calcium or vitamin D, or too high in phosphorus. It causes soft, weak bones and is common in reptiles kept without proper UVB lighting and in pets fed all-meat diets.
Signs
- Drinking and urinating more than usual
- Weakness, tiredness and reduced appetite
- Bladder stones; see dog bladder stones
- In nutritional cases, limping, swollen jaws, fractures or a rubbery jaw in reptiles
Often found by chance
Many dogs with primary hyperparathyroidism show few signs. High calcium is frequently picked up on routine senior blood work, which is one reason annual checks matter as pets age.
Diagnosis and Treatment
Vets measure blood calcium, phosphorus and PTH, and may use a neck ultrasound to find an enlarged gland. Treatment depends on the type:
- Surgical removal of the overactive gland, or ablation with heat or alcohol, for primary cases
- Managing kidney disease with diet and phosphate binders for renal cases
- Correcting the diet, adding calcium and providing proper UVB lighting for nutritional cases
See hypercalcemia for more on high blood calcium and its other causes.
Frequently Asked Questions
Is hyperparathyroidism the same as hyperthyroidism?
No. Hyperthyroidism is an overactive thyroid, common in older cats. Hyperparathyroidism involves the separate parathyroid glands and calcium control.
Can dogs recover after surgery?
Most dogs with primary hyperparathyroidism do very well after the abnormal gland is removed, though calcium must be monitored closely for a few days afterward.
Why do pet reptiles get it?
Reptiles need UVB light and a correct calcium-to-phosphorus diet to use calcium. Without them, their bones soften and the parathyroid glands overwork.
If your pet is drinking and urinating more than usual, ask about a calcium blood test. Find a veterinary clinic near you for an exam.