Feline hypoparathyroidism occurs uncommonly. It results from the end of production of parathyroid hormone (PTH). Of the small number of cases documented, hypoparathyroidism seems to occur more commonly in young to middle-aged mixed breed cats with equal representation of males and females1.
What is parathyroid hormone (PTH)?
PTH is manufactured within the cat’s parathyroid glands. These tiny glands are embedded within the two thyroid glands. All of these glands are located on the underside of the neck, just beneath the skin’s surface.
PTH is in charge of regulating blood calcium and phosphorus levels. It does so by modifying the amount of calcium and phosphorus that is:
- Absorbed by the gastrointestinal tract
- Eliminated via the kidneys
- Released from bones into the bloodstream
The results of hypoparathyroidism (too little PTH produced by the parathyroid glands) are decreased blood calcium and increased blood phosphorus levels.
Causes of hypoparathyroidism
It is unknown why the parathyroid glands spontaneously quit producing PTH. Immune-mediated destruction of the parathyroid glands (the immune system attacks the body’s own tissues) is suspected.
Damage or removal of the parathyroid glands during surgical removal of the thyroid glands is a more common cause of hypoparathyroidism. This surgery is sometime used to treat feline hyperthyroidism (overproduction of thyroid hormone).
Symptoms of hypoparathyroidism
The symptoms associated with hypoparathyroidism are the result of the abnormally low blood calcium level. The symptoms can be intermittent, particularly early on in the course of the disease. The most common symptoms include:
- Muscle tremors or twitching
- Uncoordinated gait
- Loss of appetite
- Mental dullness
Diagnosis of hypoparathyroidism
The testing typically performed to arrive at a diagnosis of hypoparathyroidism includes:
- Complete blood cell count
- Blood chemistry profile (includes calcium and phosphorus measurements)
- Ionized calcium measurement
- PTH measurement