Abnormally High levels of Parathyroid Hormone due to Chronic Kidney Failure in Cats
The excessive secretion of parathyroid hormone (PTH) due to chronic kidney failure is medically referred to as secondary hyperparathyroidism. More specifically, the cause of secondary hyperparathyroidism is absolute or relative lack of calcitriol production -- a form of vitamin D that stimulates the absorption of calcium in the intestines, calcium resorption in bone, and promotes the effectiveness of the parathyroid hormone in aiding bone resorption. Low concentrations of calcium also play a role in increased levels of PTH in blood.
The majority of symptoms relate to the underlying cause of chronic kidney failure. In some patients with chronic kidney disease, bone resorption starts around the teeth and jaw, causing a loosening of the teeth and a softening of the lower jaw, a condition known in the medical community as “rubber jaw.”
Any underlying disease that causes chronic kidney failure.
You will need to give a detailed history of your cat's health, the onset and nature of the symptoms, and possible incidents that might have led to this condition. Your veterinarian will perform a thorough physical exam to evaluate all of the body systems.
Blood testing and biochemical profiles may reveal azotemia, an accumulation of toxic amounts of nitrogenous waste products (urea) in the blood, waste products that are usually excreted in the urine and voided from the body. This condition is also referred to as uremia. There may also be abnormally higher levels of the phosphate in the blood and abnormally low levels of the calcium in the blood. For definitive diagnosis, your veterinarian will perform measurements of serum PTH concentrations. Moreover, low to normal concentrations of calcium in the blood will help in confirming a diagnosis of secondary hyperparathyroidism. Bone X-rays are also helpful in determining bone density, especially around the teeth.
Treating the underlying kidney disease is a major goal of therapy in patients that have been diagnosed with secondary hyperparathyroidism. Abnormally high levels of phosphorous in the blood is treated by using chemicals that bind to the excess phosphorous in the blood, and the diet is controlled to limit phosphorous ingestion by way of food.
To overcome calcitriol deficiency, calcitriol is given to increase calcium levels, but in very small doses that are calculated by your veterinarian based on your cat's specific need.
Living and Management
Depending on the severity of kidney failure, it is very important to check the serum concentrations of calcium, phosphorous and urea nitrogen weekly or monthly. If your cat is receiving calcitriol, you will need to closely monitor the cat's condition, as calcitriol therapy may lead to some untoward symptoms or complications.
Your cat's parathyroid hormone (PTH) concentrations will also need to be checked on a regular basis. Though renal secondary hyperparathyroidism treatment may slow down the overall progression of kidney failure, the long-term prognosis is frequently very poor in these patients.