The endocrine system consists of glands located throughout the body that secrete hormones directly into the blood. A hormone by definition is a substance that is secreted by a gland but exerts its effect elsewhere in the body. These glands include the pituitary gland in the brain, the thyroid and parathyroid glands in the neck, the Islets of Langerhans on the pancreas, the adrenal glands near the kidneys and the ovaries or testicles depending on the sex of the cat. Each of these glands secretes one or more hormones designed to produce a specific effect in the body. Dysfunction of any of these glands will produce serious systemic problems.

Diabetes is a complex, systemic disease resulting from a failure of cells in the Islets of Langerhans to produce insulin, the hormone that helps sugar move into living cells for the production of energy. Without insulin, glucose (sugar) will build up in the bloodstream and body cells will begin utilizing fats and proteins as their primary energy source. Left untreated, diabetes will be fatal, as complications from abnormal metabolism will take their toll on the internal organ function of the cat. Unlike humans, feline diabetes almost always occurs in adult, older cats. Obese cats seem to have an increased risk; some cats can develop diabetes secondary to pancreatitis and hyperadrenocorticism, but most cases are spontaneous with the cause unknown.

Clinical signs of diabetes include increased thirst, increased urination, increased appetite, lethargy and weight loss. Cataracts may develop in a few patients. In untreated, advanced cases, an unusual odor from the mouth, weakness, depression and vomiting may also be noted. Most cats are obese prior to the onset of clinical signs but then loose weight as the disease progresses. Because much sugar is passed in the urine, a lower urinary tract infection may occur. Diagnosis is based on history, physical examination and complete blood and urine testing.

A common complication is that of Diabetic Ketoacidosis, which occurs in cases of long standing untreated diabetes or where regulation of the disease is not proceeding well. As fats in the body are being utilized as a primary energy source, certain fats are metabolized into ketones. These ketones further impair metabolism and lead to acidification of the blood making the cat even more ill. Some cats may decompensate and die in a short period of time if prompt, aggressive treatment is not undertaken. Symptoms of ketoacidosis include vomiting, diarrhea, extreme dehydration, weakness and collapse in addition to the usual diabetes signs.

Virtually all cases of diabetes in cats are insulin dependent, which means that giving insulin shots, is the only way to treat the disease. While oral medications are available for humans, these are of lesser value in the cat but have been used in some cases along with careful dietary control. For general, uncomplicated diabetes mellitus, insulin injections on a set schedule, feeding a lower calorie, high fiber diet as prescribed by your veterinarian and spaying your female cat if that has not been done are all-important components to treatment.

Most people are able to learn to give the injections at home and become real "pros" in only a short period of time. Daily collection of urine and adjustment of the insulin dose may be prescribed; a fixed daily dose rarely gives top quality results but this method is often used in cats due to the difficulty in obtaining regular urine samples. The urine will contain sugars in proportion to how much sugar is in the blood. By monitoring urine sugar, the amount of insulin needed for optimal results can thereby be calculated. Periodic blood testing at your doctor's office will also be needed to check actual blood sugar levels and monitor internal organ function.

There are dozens of different types of insulin, each which acts a bit differently inside the cat. Also, not every cat responds the same; some may be resistant to the insulin and some will metabolize the insulin at different rates. Adjustments based on the response to the injections or running serial glucose tests to calculate the insulin metabolism may all need to be performed. Adjustments in diet may also come into play. The bottom line is that diabetes can be controlled with many cats having very good quality of life; in some, the process of regulation may involve a bit more work.

Treatment of Diabetic Ketoacidosis is slightly more difficult. More severe systemic involvement produces the need for intensive care to restabilize the patient and restore normal metabolism. Most cats are hospitalized, placed on intravenous fluids, electrolytes and bicarbonate therapy to counteract the acidosis of the blood. Regular insulin, which is more rapid acting, will be given, then, as the patient stabilizes, longer lasting insulin treatment will start. Careful care and monitoring is essential for these patients, but if successful, most cats can return to normal home insulin therapy.

Hyperthyroidism is a serious and relatively common endocrine disorder resulting from excess in thyroid hormone in the circulation. Most commonly, this condition is caused by a functional (hormone producing) enlargement of the thyroid gland(s) or a hormone producing thyroid tumor. Fortunately, the more serious thyroid carcinoma rarely produces this condition in cats. In about 70% of cats, both thyroid glands will be enlarged and/or contain tumor tissue. The other 30% will have one-sided involvement. As to how or why these enlargements or tumors appear is uncertain, but this condition has been seen more frequently in the last two decades. ((Thyroid Gland)) 

Because thyroid hormone exerts a profound effect upon the metabolic rate of all cells in the body, cats with this condition are literally running at "top speed" all the time, which is ultimately quite detrimental to the health of the animal. Clinical signs include weight loss, an increased if not ravenous appetite, vomiting which may be intermittent, increased thirst and urination, increased activity levels, hyperactivity, restlessness, diarrhea, an unkept and possibly matted haircoat and a rapid, pounding heartbeat. As the disease progresses and the body literally becomes worn down, further signs will include weakness, panting, trouble breathing, increased stool output and loss of appetite.

Diagnosis is based on history, physical examination, blood counts, serum chemistries, urinalysis, thyroid testing, EKG analysis and in some cases, the use of radioactive imaging may be employed. Many cats suffer liver and heart damage from this illness, but with proper treatment may be able to heal and do well. Early and aggressive diagnosis will give most cats a chance for treatment to be quite successful.

There are three options with regards to treatment of this condition: Antithyroid drugs, which suppress the production/secretion of thyroid hormone can be used, either to help stabilize a cat prior to surgery, on a long term basis where surgery is not performed, or in cases where surgery has not been 100% successful. Methimazole and Propylthiouracil are the two drugs commonly employed. Some cats, often due to more serious heart changes secondary to this disease, may not be very good surgical candidates yet may improve and do quite well on this therapy on a long-term basis.

Cats so treated can experience side effects including loss of appetite, vomiting, weakness and some rare blood diseases. Over time, many of these cats will experience a recurrence of the symptoms of the disease. All cats need to have regular blood and thyroid testing while on these medications. Otherwise, many cats can be maintained relatively well with these drugs.

Although more aggressive an approach, surgical removal of one or both affected glands is very effective in controlling if not even curing the disease in many cats. Known as a thyroidectomy procedure, the surgery is relatively simple and as mentioned, often very successful. What is not simple about this surgery is that many cats suffer from heart, liver and intestinal changes associated with hyperthyroidism, which make such patients more of a surgical/anesthetic risk. In this author's hands we have had a success rate over 95%, even in some very critical patients. Many cats are given anti-thyroid medication for a few weeks prior to surgery to stabilize them and careful anesthetic and support care is critical for success. Deaths do occasionally occur when attempting this procedure.

Also, in cats where both thyroid glands are involved and thus, need to be removed, it is essential to preserve at least one of the four closely associated parathyroid glands to avoid the cat having a hypoparathyroid crisis. Careful skill and keen surgical vision is essential to maintain parathyroid gland function for these cats. Post surgical thyroid monitoring and nursing these cats back to full strength will bring many cats near their former body condition.

The third option currently available for hyperthyroid cats involves the use of radioactive iodine which, when injected into the cat will be absorbed into the thyroid gland and selectively destroy that tissue. Usually only the abnormal tissue will be destroyed using this technique. While this technique is quite simple and relatively free from side effects, there are only certain facilities able to handle the radioactive materials properly making availability more limited.

Low production of thyroid hormone is a very rare disorder in the cat. Most cats diagnosed with the condition are young, thus having a congenital form of the disease. Unfortunately, many of these kittens die before a diagnosis can be made. The only other time this disease is commonly seen is after surgery for hyperthyroidism where both thyroid glands are removed. As thyroid hormone is responsible for controlling the metabolic rate of cells in the body, when the hormone is absent, the normal function of most every cell in the body declines.

Clinical signs of hypothyroidism include poor growth and development in young kittens, dwarfism, poor hair growth, lethargy and mental dullness. In adult cats, symptoms can include lethargy, dullness, hair loss on the earflaps and back, scales on the skin, mats of the coat due to poor grooming and obesity. Symptoms present will vary greatly in severity between cats. Diagnosis is based on the history and clinical signs, blood testing, serum thyroid testing, or more specialized thyroid stimulation tests. There are other factors and diseases that can also influence and reduce the production of thyroid hormone.

Daily or twice daily oral thyroid replacement works well for most cats and is relatively inexpensive. Obese cats should be placed on a reducing diet to speed weight loss and your veterinarian should have several from which to choose. Proper levels of exercise, control of treats a cat receives and regular follow-up exams and monitoring of blood thyroid levels will help provide a good long-term prognosis for most pets.

The adrenal glands secrete several steroidal hormones that perform various functions in the body. Hypoadrenocorticism occurs if the adrenal glands, for whatever reason, decrease or cease to secrete these hormones. The severity of the disease will vary and can mimic other conditions including renal or gastrointestinal disease.

Clinical signs include lethargy, weight loss, loss of appetite, increased thirst and vomiting. These signs seem to wane and wax in many cats so affected. Weakness, dehydration, low body temperature and collapse occur less commonly. Not all symptoms will occur in every case, nor with the same severity as previously mentioned. Diagnosis is based on history, clinical signs, blood counts, serum chemistries, urinalysis, X-rays, EKG testing and special testing to determine how the adrenal glands are functioning.

Cats with mild clinical signs can often be treated with oral prednisolone and flurocortisone in combination to replace missing endogenous steroids. Long term regular blood monitoring will be needed to gauge the amount and frequency of oral medication, but most patients do very well once stabilized.

Cats that present with severe weakness or acute collapse are in serious condition and require immediate hospitalization. Intravenous fluids to correct fluid and sodium deficits are necessary and injections of dexamethasone and DOCA as initial steroid replacement are needed to stabilize the patient. Most cats respond well in 24-48 hours and can be switched to oral medications for long term use. Cats that have been on medication then stop may collapse as described and need this intensive care to return too normal.

An increase in glucocorticoid (cortisone) output by the adrenal gland is known as hyperadrenocorticism, a disease not commonly seen by veterinarians. The abnormalities associated with this condition are due to long term internal exposure to high levels of cortisone. While cats are more resistant to the effects of cortisone than are humans or dogs, there are detrimental effects noted. The disease may occur due to pituitary gland dysfunction, adrenal gland tumors and even secondary to conditions where cats have been taking oral steroids for long periods of time. Older cats most commonly acquire this condition.

Felines with Cushing's disease will show signs of drinking and urinating much more than normal, have a bloated and pendulous abdomen, have loose hair over both sides of the back and trunk, the skin will tear easily, appetite will increase, muscles will atrophy somewhat and most will loose weight over time. It is not uncommon for these cats to also develop diabetes mellitus as the disease progresses.

Diagnosis is based on these clinical signs, blood, serum and urine analysis, X-rays and special testing of the adrenal and pituitary gland function to secure the diagnosis and pinpoint the cause of the illness. The easy tearing of the skin is very significant and important as an indicator of this disease in cats.

Long term treatment and management of this syndrome is difficult and sometimes only partially successful. Complications and secondary illness is not uncommon and these need specific treatment. The use of mitotane, which destroys part of the hyperfunctional gland, is used in dogs but can be dangerous to cats. Ketoconazole, an anti-fungal medication, has been used with good success. A new drug, Anaparil, works well in dogs but is not approved for use in cats. Surgical removal of all or part of affected adrenal glands is possible but the surgery is difficult and risky for most surgeons to perform.

Frequent and repeated blood and serum testing, including the adrenal function test is necessary to fine-tune the therapy for optimal results. In the early stages of treatment, tests may be needed every few weeks, but your veterinarian will need to individualize a plan to best fit your cat's problem. Secondary diabetes needs to be controlled and will only make stabilization more difficult. Long term survival after diagnosis of 1-2 years is considered good.

The parathyroid glands consist of two very small glands on each lobe of the thyroid gland, hence, the name. These glands control calcium balance in the body by secreting parathyroid hormone, which increases blood calcium and the hormone calcitonin, which decreases blood calcium levels. Blood phosphorus levels are partially controlled this way as well and vitamin D also plays a role in this regulatory mechanism.

Conditions of the parathyroid glands are very rare. Hyperparathyroidism may occur if excess parathyroid hormone is secreted. This is usually secondary to parathyroid tumors and the symptoms of illness are usually related to calcium levels in the blood being consistently elevated. Another condition, known as nutritional hyperparathyroidism, can also produce symptoms related to abnormal blood calcium levels but the cause of this condition is dietary. Clinical signs include increased thirst and urination, poor appetite, weight loss, lethargy, weakness, muscle twitching, seizures and constipation. Many animals may be without symptoms with the disease being diagnosed during other testing. Often physical examination will be quite normal.

Diagnosis is based on this history, physical examination, blood and serum testing, X-rays, ultrasound and exploratory surgery. Quite a few other conditions may cause abnormal increases in blood calcium levels including various types of tumors, hypoadrenocorticism, renal failure, the increased intake of vitamin D and certain bone diseases. All these need to be explored and ruled out before making a diagnosis of hyperparathyroidism.

Low blood calcium (Hypoparathyroidism) is most commonly associated with eclampsia, enema toxicity, renal failure, low blood protein levels, pancreatitis, malabsorption syndromes or after some type of internal or surgical destruction (post thyroidectomy) of the parathyroid and/or thyroid glands. Signs of low blood calcium can be severe and include nervousness, tremors, twitching, muscle spasms, staggering when walking, panting, weakness, increased thirst and urination, vomiting, diarrhea, weight loss, anorexia and depression. Diagnosis is based on this history, physical examination, blood and serum testing, X-rays, ultrasound and exploratory surgery.

Treatment centers first on identification of the primary cause of the calcium variations in the blood. Primary parathyroid gland tumors may be surgically treated. Cats with low blood calcium may need intravenous and oral calcium, with calcium and vitamin D supplementation that may continue for the life of the pet.

The pituitary gland is a small multi-part gland located at the base of the brain near the optic nerves. The pituitary gland's main function is to measure hormone levels in the blood from other endocrine glands and secrete other hormones as needed to turn the various glands on or off as required. The Islets of Langerhans, however, are not regulated in such a fashion.

Disease, dysfunction or tumors of the pituitary gland can lead to dysfunction of any or all of the other endocrine glands producing disease specific for each individual organ. Other conditions such as abnormalities in growth can also occur due to pituitary dysfunction. These conditions are uncommon, diagnosis is complicated and treatment options are often limited to specific endocrine glandular disease.

...covered in the MALE REPRODUCTIVE section or

the FEMALE REPRODUCTIVE section

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