Diseases of the endocrine system (the “glands”) are common in cats. Last month, we discussed hyperthyroidism. This month, we will discuss Diabetes mellitus.  Diabetes mellitus (DM) is a common feline endocrinopathy. A survey of private practices showed a prevalence of rate of 1 in 180 cats. During 1970 to 1999, there was an increase from 8-124/10000 cases.

The classic diabetic cat is usually an overweight, middle aged male cat which presents because the client has noticed that their kitty is losing weight, isn’t quite him/herself and may show an increase in appetite, urination and/ or water consumption. Less commonly, the kitty may be anorectic or inappetant. Kitties may be obese in the early stages and as with hyperthyroidism, diabetes must be a concern if an otherwise healthy kitty presents for weight loss yet hasn’t been on a weight loss program. A severe form of diabetes in which there are ketones in the system, is seen and these cats are severely sick and often constitute as a medical emergency. Signs of diabetic ketosis include dehydration, lethargy, weakness, anorexia, vomiting and diarrhea. In order to confirm a diagnosis, lab work checking glucose values in blood and urine as well as an elevated fructosamine will be performed.

The most common form of diabetes in kitties is a result of B-cell loss with decreased insulin secretion and /or peripheral insulin resistance. This scenario is usually associated with islet-associated amyloidosis. Other causes of DM include drug induced insulin resistance (glucocorticoids, progestins), acromegaly, hyperprogesteronemia, hyperadrenocortism and pancreatits.

The goals of treatment for diabetes mellitus are to minimize clinical signs of diabetes, reduce the risk of hypoglycemia and prevent development of long term complications. Treatment usually involves giving insulin, controlling diet with a low carb/high protein diet and control or resolution of concurrent precipitating factors. Many kitties may “go into remission” when managed this way which implies that there are still functioning islet cells. Perhaps these cells can be spared and function will resume function after the affects of glucose toxicity have been reduced. In contrast, oral hypoglycemic agents that have been used in cats apparently stimulate insulin release from residual B-cells and have the potential to exhaust those cells as opposed to “sparing” them. Oral agents also have the potential to worsen amyloid deposition in the pancreas. For this reason, all diabetic cats should be started on a low-carbohydrate, (canned), diet and insulin in order to blunt the effects of glucose toxicity and increased B-cell attempts at insulin production. In any case, the prognosis for diabetes mellitus in cats depends on the cause, an early diagnosis, and adequate therapy.

Insulin therapy in cats can be frustrating due to the cat’s unique metabolism. Compounding the problem is that the form of insulin kitties require is not commonly used in human medicine so insulin production is often discontinued. Currently, in the USA, there is an approved insulin for use in cats, vetsulin. Additionally, glargine (lantus) is also being used. Both insulins have their pros and cons and having options helps with managing different cats.

In non-ketotic patients, kitties are usually started on Vetsulin or Glargine. Both are given every 12 hours. They are a different concentration and it is very important to verify syringe size. Vetsulin is a U-40 insulin and is an intermediate acting of pork insulin origin. It is most like feline insulin and may allow easier dose adjustments. Many cats are very responsive to this insulin to the point of increased risk of hypoglycemia so in those patients, we commonly switch to Glargine (Lantus). Additionally, intermediate insulins may not provide long enough duration in some cats.   Lantus is a long acting, human recombinant U-100 insulin. It is in the same category of the old feline standby of PZI. It commonly provides a very steady state of glucose activity yet due to its long duration of action may result in cumulative hypoglycemia. Short acting, regular insulins are U-100 and are used to stabilize a ketoacidotic patient prior to starting on long term insulin.

For monitoring diabetic control, the history and physical exam seem to be the most important. If the kitty is not pu/pd, not losing weight (unless on a diet), and not having episodes of hypoglycemia or hyperglycemia, the diabetes is most likely well controlled at this time. Ten-12 hour glucose curves (may be longer with Glargine), combined with fructosamine are used to evaluate response to insulin and to make adjustments. The curve tells us how the kitty is responding over daily time and fructosamine tells us how things are going over extended time and to monitor for prolonged hypoglycemia. Combined with clinical signs, these methods are the hallmarks of monitoring and are necessary in all diabetic cats.   Urine monitoring is also used in specific kitties based on need, especially kitties that have been in remission; it assists with identifying when they come out of remission. Owners are requested to maintain a diary and monitor for signs of hypoglycemia and/or hyperglycemia.  Owners are not to make adjustments without speaking to the Doctor first.

Curves are initially done around day 5-7 after starting insulin and then every 10-14 days over a period of 2-3 months. After stabilization, checks will be extended for long term management, incidence monitoring and for evaluation of general body health. It is very important to remember these cats can still develop other problems and not to just focus on the diabetes.

Owners play a huge role in the health and well-being of their diabetic kitties. They are the first line of communication with the veterinarian regarding their kitty’s health and their kitties depend on them for their proper diet, injections and monitoring. With steady, dedicated care, many of these kitties will live comfortable lives with little disruption to normal daily activities.   Owners play a huge role in early diagnosis and for bringing kitties in at least twice yearly for health examinations and appropriate lab monitoring.