Hyperparathyroidism in Cats

Hyperparathyroidism in cats is characterized by elevated parathyroid hormone levels. It is an endocrine disorder that develops when the parathyroid glands release an excessive quantity of parathyroid hormone, which causes the body to become dehydrated.

Cats have four tiny parathyroid glands, which are positioned adjacent to the thyroid gland in the feline’s neck. The prefix para- alludes to nearby or beside, while thyroid refers to the real thyroid gland; the thyroid and parathyroid glands are placed side by side in the neck, near the windpipe or trachea, and are responsible for producing thyroid hormone.

Increased activity of one or more of the parathyroid glands results in excessive production of the parathyroid hormone, which is essential for maintaining the proper balance of phosphorus and calcium levels in the blood. It is possible for calcium levels in the blood to fall too low before the production of parathyroid hormone increases, which permits calcium to be removed from the bones to maintain the proper calcium levels.

Symptoms of Hyperparathyroidism in Cats

Symptoms will not appear until the blood calcium levels have been elevated for a prolonged time, as in the case of kidney failure. Here are some of the symptoms:

  • Excessive thirst
  • Excessive urination
  • Appetite loss
  • Loss of weight
  • Weakness
  • Drowsiness
  • Sluggishness
  • Exercise intolerance
  • Suffering from stupor or coma
  • The presence of kidney stones in the urine tract
  • Vomiting
  • Constipation
  • Muscle mass loss Stiffness in the gait
  • Bloody Urine


There are two types of hyperparathyroidism:

  • Primary hyperparathyroidism
  • Secondary hypoparathyroidism

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Primary Hyperparathyroidism

Primary hyperparathyroidism is a condition in which a tumor in the parathyroid gland causes the production of abundant amounts of parathyroid hormone, resulting in raised calcium levels in the blood. The parathyroid glands, which have been four tiny glands located next to the thyroid gland, help regulate the thyroid’s function. When it comes to finely managing the calcium level in the blood, these tiny glands play a critical role.

The cat’s parathyroid glands are divided into two groups: the exterior parathyroids and the internal parathyroids. The external parathyroid glands are positioned outside the capsule that surrounds the neighboring thyroid gland, but the internal parathyroid glands are embedded within the thyroid gland itself.

The parathyroid glands generate a hormone known as parathyroid hormone, which is not unexpected given its function. This hormone is the most important hormone to consider in the exact, minute-to-minute regulation of calcium content in the blood.  The body’s purpose is to keep the calcium level in the blood within a small range at all times. Because of their extreme sensitivity to calcium levels when the calcium level declines. When this occurs, the parathyroid glands secrete parathyroid hormone (PTH). This results in several difficult outcomes, including:

  1. PTH stimulates the release of calcium from the bones into the blood stream.
  2. The hormone PTH stimulates the development of an enzyme in the kidneys that aids in the creation of calcitriol, a hormone that regulates calcium metabolism. Calcitriol stimulates the absorption of calcium (and phosphorus) from the diet by increasing the amount of calcium absorbed.
  3. The hormone PTH stimulates the kidneys to absorb additional calcium from the urine while excreting all of the excess phosphorus that has been absorbed from bones and the digestive tract.

This procedure’s end consequence is that an average calcium level is restored. When the calcium level returns to normal, the parathyroids get a signal that “mission accomplished” has been achieved, and they lower the amount of PTH secreted.

How It Occurs?

It is possible to develop primary hyperparathyroidism if one of the parathyroid glands secretes large levels of parathyroid hormone (PTH) on its own. The source of the increased secretion is generally a benign tumor of one of the glands — known as an adenoma — although in rare cases, the tumor is a malignant carcinoma that must be removed. Cats affected are often older, with an age range ranging from eight to fifteen years old on average. The clinical indicators are typically non-specific and include tiredness, a low appetite, vomiting, and nausea.

Cats are generally unimpressive physically, with the only constant observation being the presence of an enlarged parathyroid gland in the neck (in approximately 50 percent of the cases). A high calcium level will be detected with routine blood testing.

Because PTH stimulates the excretion of phosphorus by the kidneys, some cats with primary hyperparathyroidism will have low serum phosphorus concentrations. In certain cats, excessive calcium levels will result in the production of calcium oxalate stones in the bladder due to the increased calcium levels. Symptoms associated with this condition include increased frequency of urination, straining to urinate, peeing in inappropriate areas, and the presence of blood in the urine.

How Is It Diagnosed?

The determination of the blood level of parathyroid hormone (PTH), as well as the determination of serum ionized calcium, are required for the definitive diagnosis of primary hyperparathyroidism (iCa). The use of ionized calcium allows for a more precise determination of the calcium status. The diagnosis is correct if both the PTH and iCa levels are elevated. According to the results, if the iCa is high and the PTH is in the upper half of the reference range, the cat is most likely still suffering from hyperparathyroidism. When the calcium level is elevated, the parathyroid gland’s normal response slows down the synthesis of parathyroid hormone (PTH). The presence of a parathyroid hormone (PTH) level in the upper half of the reference range in the presence of high calcium is an inappropriate reaction, signaling that the parathyroid gland has gone wild and is secreting the hormone autonomously.

Parathyroidectomy is the most generally suggested therapy for primary hyperparathyroidism, which removes the aberrant thyroid gland from the body. The use of ultrasound in the neck can assist in determining the specific position of the tumor, such as whether it is in one of the exterior parathyroids or one of the internal parathyroids. This enables thorough pre-surgical planning to take place. Anesthetic problems associated with excessive calcium levels include an unusually slow heart rate, high blood pressure, and cardiac arrhythmias, making cautious anesthetic planning a must-do for every patient.

Parathyroid tumors affecting one internal parathyroid gland are more difficult for the surgeon to detect than external parathyroid tumors. Removing the entire thyroid gland lobe is necessary if internal parathyroid is involved, which is rare. In dogs, a type of therapy known as chemical ablation has been developed, including injecting ethanol into the aberrant gland to cause it to shut down completely.

Post-operative problems are rare, but the most prevalent is a low calcium level, which is paradoxical given the procedure’s focus on calcium. (However, this is a more severe issue in dogs than it is in cats.) A tumor in one parathyroid gland, as previously indicated, causes an excessive amount of PTH to be produced, resulting in atrophy of the remaining parathyroid glands. The removal of the problematic gland will result in a quick decrease in PTH levels in the blood.

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Secondary (Nutritional) Hyperparathyroidism

Nutritional or secondary hyperparathyroidism is a dangerous condition that develops as a direct result of feeding diets that are either too low in calcium or too rich in phosphorus in animals’ diet. The mineral imbalance that results causes the bones to become dehydrated and brittle (osteopenia). When the body’s bones become weak, painful, and prone to fracture, it manifests itself in a slew of severe clinical indications. Additional metabolic disorders may accompany the sickness.

Clinical indications of nutritional secondary hyperparathyroidism in pups and kittens are often associated with reduced bone density and osteopenia, which is true for both breeds. Animals affected may be reluctant to move, and their limbs will be uncomfortable when touched. As a result of a calcium deficiency in the bones, pathologic and painful fractures of the limbs can develop, causing significant discomfort. Additionally, neurological indications are possible that are directly connected to low blood calcium levels, such as seizures or muscle twitching. Fractures of the vertebral body do occur on rare occasions, and the accompanying instability inside the vertebral canal can cause direct damage to the spinal cord, resulting in paresis or complete paralysis.


The diagnosis of this condition is frequently made based on clinical indicators and a discussion of food, although further diagnostic tests are frequently required. It is essential to obtain radiographs of the afflicted limb in order to rule out pathologic fractures if your pet exhibits indications of lameness or discomfort when a limb is palpated. On radiographs of afflicted animals, the presence of osteopenia (bone loss) is readily discernible.

Blood tests can also be used to confirm a diagnosis in some cases. Calcium levels in the blood may be normal or low, but phosphorus levels may range from low to high. PTH levels in the bloodstream may also be increased. Other biochemical measures are generally within normal limits, except for a slight rise in alkaline phosphatase in some instances.

Causes of Hyperparathyroidism in Cats

Primary hyperparathyroidism has been caused by one or more benign tumors, known as adenomas, that develop on the parathyroid gland and cause the gland to overproduce calcium. The tumor causes the parathyroid to release an excessive amount of parathyroid hormone, which is harmful. Cats are highly unlikely to develop malignant parathyroid tumors.

When a dietary deficiency or other problems are present, secondary hyperparathyroidism results. Secondary hyperparathyroidism can be caused by a variety of factors, including:

  • Kittens who are given a diet consisting solely of flesh
  • Calcium and vitamin D inadequacy as a result of a poor diet
  • The presence of an overabundance of phosphorus in the diet
  • Chronic kidney disease is a medical condition that occurs over time.

Secondary hyperparathyroidism is associated with both long-term (chronic) renal damage and acute kidney injury. Because of a deficiency in calcitriol (a hormone that regulates calcium levels and absorption in the intestines) produced by the kidneys, calcium is lost, and calcium absorption is reduced through the intestinal tract. This may also be due to the retention of phosphorus in the body, which can cause calcium loss through the kidneys and absorption of calcium through the intestinal tract to decrease.

Diagnosis in Cats with Hyperparathyroidism

  • It will be necessary to provide the veterinarian with the cat’s entire medical history, an estimate of when the symptoms first appeared, and a thorough record of all of the symptoms. This will entail feeling for an enlargement of the parathyroid gland, examining for muscular and gait irregularities, as well as listening to the cat’s respiration and heart rate. The veterinarian will also do a mental examination of the cat.
  • Lab tests will be conducted, including a full blood count, a biochemical profile, and a urinalysis. These tests will reveal the amounts of calcium and phosphate in the blood and urine, as well as whether or not the renal disease is present. A positive test for hyperparathyroidism will confirm the diagnosis of the condition. Additional tests will be carried out in order to ascertain whether a tumor or a nutritional deficit is the source of the problem. It will be necessary to examine the thyroid and parathyroid glands using ultrasound and X-ray technology. These examinations will be performed to determine whether or not a tumor exists. Other blood tests may be conducted to detect whether or not there are any nutritional deficiencies in the body.
  • Because the parathyroid gland is so tiny, it may be required to do exploratory surgery to locate the tumor and diagnose the origin of the hyperparathyroidism in some cases.

Treatment of Hyperparathyroidism in Cats


Removing the gland producing the high hormone release is one of two choices for treating primary hyperparathyroidism. Surgery is one of the two procedures for removing the gland. Before the procedure, the cat will be required to fast. Before performing the procedure, the veterinarian will provide a general anesthetic to the cat and make a tiny incision on the underside of its neck, which will allow him to expose and remove the gland.

Treatment with alcohol or heat

The second option for eliminating tumor-bearing parathyroid glands is to use alcohol or heat therapy as a treatment. Compared to surgery, these methods are less intrusive. A 90 percent success rate for alcohol therapy is achieved, whereas a 50% success rate is achieved with heat treatment. A needle will be placed into the gland with the help of an ultrasound to ensure proper placement. The administration of alcohol or heat will be attempted to kill the gland, which will result in the cessation of excessive secretions. Hospitalization is required for both surgical procedures and alcohol or heat treatments. It will be necessary to constantly monitor the cat’s calcium levels as a result of the abrupt decline in produced parathyroid hormones. Calcium supplements may be required until the body can control its own calcium levels.

Dietary Modifications

In order to treat secondary hyperparathyroidism, it is necessary to address the dietary inadequacies that resulted in the excess levels in the first place. If the cat has nutritional inadequacies, the veterinarian will recommend a specific cat food and maybe extra vitamins to rectify the situation.

Treatment for Chronic Kidney Disease

Chronic renal disease in cats that manifest with hyperparathyroidism will necessitate medication administration to treat the cat’s kidney disease. This may entail the administration of medicines as well as the establishment of a low-phosphorous diet.

Recovery of Hyperparathyroidism in Cats

The kitty will need to follow up with the veterinarian to keep track of its calcium and phosphorus levels while being monitored by the government. After receiving alcohol or heat therapy, cats will require repeated ultrasounds and testing to verify whether or not the gland has been appropriately removed. In the event that the treatments are unsuccessful, surgery will be required. The veterinarian will also need to check in with the cat if it has a chronic renal disease frequently to ensure that its kidney function is being appropriately checked. Cats suffering from hyperparathyroidism have a favorable prognosis if they get correct therapy.


There are currently no effective techniques for preventing primary hyperparathyroidism; however, an appropriate diet can help avoid secondary hyperparathyroidism caused by starvation.

Living and Management

When one or more parathyroid glands are surgically removed to treat primary hyperparathyroidism, low calcium levels in the blood (hypocalcemia) are relatively common. This is especially true in individuals with presurgical calcium values of more than 14 mg/d. If your cat has had surgery, your veterinarian will want to monitor serum calcium concentrations daily for at least two weeks following the procedure. He or she will arrange frequent blood tests to check on the well-being of the kidney.

Home Care of Cats With Hyperparathyroidism

To provide the best possible therapy for your pet, a combination of at-home and professional veterinary care is required. Following up with your pet is essential, significantly if he or she does not improve quickly.

  • Administer all recommended drugs exactly as suggested by your doctor. If you have difficulties treating your pet, contact your veterinarian right away.
  • Recommend that customers keep a careful eye on their dogs during the critical first one to seven days following surgery for indications of low calcium, including panting, agitation, muscle twitching, leg cramps, stiff walk, or seizures.
  • Seek frequent medical attention and blood testing from your veterinarian to ensure that calcium levels remain within normal limits and to monitor any damage that may have happened to other body systems, particularly the kidneys.
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