Somogyi Rebound in Feline Diabetes

Contrary to what common sense would tell us, there are times when the best solution to high blood glucose numbers is to give LESS insulin. This instinctively seems wrong. However, there is very interesting physiology to explain this phenomenon.

In a non-diabetic, there are two hormones that maintain blood glucose levels. These are insulin, and glucogen, both produced by the pancreas. Insulin allows the body to use sugar in the blood or to store it for later use. Glucagon is basically offering a moderating effect to insulin by causing cells to release glucose. Therefore, in a non diabetic, if the blood sugare goes too low, the glucagon will utilize some of the stored glucose. These hormones work together to moderate blood sugar levels.

In a diabetic cat, if the blood sugar drops too low or drops too quickly, the glucagon causes the liver to indiscrimintely dump glucose into the bloodstream. This causes the cat to become hyperglycemic (high blood sugar). It is the body's self defense mechanism to stop hypoglycemia(low boood sugar). This is a simplistic description of the phenomenon as there are other hormones and biochemical processes involved, however this is essentially the mechanism.

This sharp drop followed by unusually high blood glucose levels is known as Somogyi rebound.

Because of all the hormones involved in this process, this rebound may last several cycles,
punctuated by higher blood glucose levels. The blood glucose curves will possibly be flat and high, which normally indicates that more insulin is required. However, this is not the case and the treatment for somogyi is a REDUCTION in insulin, to stave off the precipitious drops that start the whole cycle.

Somygi is difficult to detect but if you are having trouble regulating your cat despite increasing insulin levels, please discuss with your veterinarian the possibility of somogyi rebound.

Types of Insulin Used to Treat Feline Diabetes

There are many different types of insulin used to treat feline diabetes. Part of the trick of feline diabetes is that none of these insulins are exactly like cat insulin. You must find, through trial and error, the best insulin for your cat.

Many vets prescribe human insulins. These are cheap and easy to get and work very well for many cats. Humulin N, L and U are three that are typically prescribed. The N insulin is a short acting insulin and probably does not have enough duration for most cats. It can have sharp steep drops (where the blood sugar drops too low) and then it can wear off quickly causing the blood sugar to increase quickly. L and U (Lente and Ultra lente) are medium and longer lasting insulins. Unfortunately, Eli Lilly, the manufacturer has discountinued these and many people whose cats have been regulated on these are scrambling to find alternatives.

Caninsulin is a pork based insulin which is prescribed by the veterinarian. It is considered a medium acting insulin. This is also knows as Vetsulin in the United States.

Lantus is a newer human insulin that has some promising research done on cats. It is very long lasting insulin.

PZI is another insulin and it can be found in a pork or beef format. The insulin is in a protamine zinc suspension, which makes it a long lasting insulin as well. Many cats do well on the beef derived PZI.

More history of Kitty and his feline diabetes

As part of my blog, I am trying record of what is happening with my cat, Kitty. Kitty is a 15 year old tabby, weighing in at 23 pounds. As I mentioned before, he was first diagnosed with feline diabetes back in January of 2o01 but "snapped out of it" (so to speak) by June 2001.

Fast forward to Octiber 2005, and his diabetes is back!! We started on the animal insuln, Caninsulin which proved to be a disaster. On January 18th, 2006, we switched to a human insulin called Lantus. It is a long lasting insulin, which has shown much promise in studies to be good for cats. One of the biggest problems with administering insulin is that there is no insulin out there that is EXACTLY LIKE FELINE INSULIN. Often, cats do not respond well or at all. Even when they do respond, their bodies need time to get used to this new insulin and figure out how to use it. Therefore, each dose should be allowed to settle for at least 7 days.

We started at a conservative dose of 2.5U Lantus, twice a day (also known as BID). The vet wanted us to start at 5U BID, but I have seen Kitty's numbers crash and really wanted to be careful. We stayed on this dose for approximately 2 weeks, but saw no real improvement. We then increased to 3.5, 4.5 and finally, as of last Tuesday, we are at 5U BID. One issue we have noticed is that Kitty is getting serious neuropathy in his back legs. It is caused by nerve damage due to high blood glucose levels.

I test Kitty's blood glucose before every shot. Normally, his numbers are very high (26, 30 etc). A normal range is 4-8 mmol/dl. Last Wednesday, his preshot was 15. I gave him his full dose and watched as his sugars dropped to 2.9 before they started to climb back up. Usually, the climb up much higher. This is possibly an instance of symogi or rebound (more on rebound later). His next preshot was 23.9.

Thursday night, his preshot was 9.3 mmol/dl!!! He was playing with the laser pointer and being very "himself". In this instance, the best thing to do is to feed and test again in an hour. Well, an hour later, he was at 5.4! By 3 hours past his normal shot time, he was only back up to 8 and 8 hours after, we was only back up to 17. By the next morning, he was at 28.9 and we have not been able to move that much.

Hopefully, we can straighten this out a bit better this weekend.