Hyperparathyroidism in cats is a disease in which the parathyroid glands become overactive and produce excess parathyroid hormone. It's important to note that the parathyroid glands are distinct and separate from the thyroid glands. The hormone they produce helps to maintain levels of calcium and phosphorous in your cat's blood. If blood calcium levels drop, your cat will suffer bone damage as his body removes calcium from the bones and teeth to make up for low blood calcium levels.
The Feline Parathyroid Gland
Your cat's parathyroid glands are located next to, and sometimes even inside, his thyroid gland. The thyroid gland is located in your cat's throat. When the parathryoid glands produce too much parathyroid hormone, the resultant disease is known as hyperparathyroidism; there are two kinds of hyperparathyroidism, primary and secondary.
Primary Feline Hyperparathryoidism
Primary hyperparathyroidism happens when one of your cat's parathyroid glands falls victim to cancer or begins to overproduce parathyroid hormones for another reason. As a result, blood calcium levels rise. This type of hyperparathyroidism is most common in geriatric cats.
Symptoms of hyperparathyroidism include:
- Vomiting
- Excessive thirst and urination
- Loss of appetite
- Lack of energy
- Depression
The symptoms of primary hyperparathyroidism develop slowly over time, so that the disease has usually progressed quite far before symptoms become noticeable. Treatment involves removing the damaged gland. Your cat may suffer dangerously low levels of blood calcium immediately following such a surgery. He'll need to be closely monitored in the clinic and given calcium supplements if his blood calcium level drops too low.
Secondary Feline Hyperparathryoidism
Secondary hyperparathyroidism in cats has a dietary cause, and usually occurs in young kittens who have been fed an all meat diet, or any diet with an inappropriate balance of the minerals calcium and phosphorous. An all meat diet contains high amounts of phosphorous and very low levels of calcium. Cats are meat eaters, but they also need to consume the bones of their prey in order to get their dietary calcium requirements.
Secondary hyperparathyroidism occurs because, when blood calcium levels are chronically low due to nutritional deficiency, your cat's parathryoid glands will produce excess parathyroid hormone and begin to leech calcium from your cat's bones and teeth.
Kittens with secondary hyperparathyroidism develop weak bones. They may seem unwilling to move, and may assume a splay-legged posture. Their thin bones will break with ease. They may also develop abormalities in bone growth, due to inadequate bone density. Bone growth abnormalities occur mostly in the spinal column and pelvis, which places undue strain on the joints and may lead to arthritis.
Any skeletal deformities that occur as a result of secondary hyperparathyroidism are usually permanent, and cannot be corrected even with surgery. The hormone imbalance can be corrected by placing the kitten on a balanced diet. Kittens who have suffered bone damage due to hyperparathyroidism may need lifelong treatment for any complications that develop.