Pets with Diabetes: Somogyi Rebound

Definition
Somogyi rebound is one of the body's natural defense mechanisms to protect itself against hypoglycemia. It can occur when the blood glucose is too low, or if the blood glucose is above "normal" but drops too quickly.

A non-diabetic maintains normal sugar metabolism using two major hormones. The first is insulin, which lowers the blood glucose by allowing cells to remove glucose from the blood and either use or store the glucose. The second hormone used to regulate sugar metabolism is glucagon. Like insulin, glucagon is produced by the pancreas. Glucagon has the opposite effect of insulin. Glucagon causes cells to release glucose, thus causing the blood glucose to increase.

When the blood glucose becomes too low, the body's natural defense mechanism is to release glucagon and several other hormones into the blood. The overall effect of these hormones is to increase the blood glucose. Glucagon causes the liver to rapidly release large amounts of stored glucose into the blood stream. After all this glucose is released into the blood, the animal can become hyperglycemic (high blood glucose). The other hormones involved in this protective mechanism act to keep the blood glucose elevated for a longer period of time.

Because Somogyi involves several other hormones that have a longer duration of action than glucagon, the hyperglycemia caused by a Somogyi may last for several days and you may see insulin resistance. This can make diagnosing somogyi difficult.

Somogyi bg curve
Figure 1 shows a hypothetical Somogyi rebound. The green line show the bg curve when an appropriate insulin dose is given and the red line shows the Somogyi rebound that can occur when too much insulin is given. Thanks to Brenda and Cody for data for this graph.

Somogyi Sample BG Curve

When does a Somogyi Rebound happen?
If an animal experiences hypoglycemia, or if the blood glucose drops drops too quickly, the body tries to protect itself using the Somogyi response and the result is elevated blood glucose, or hyperglycemia.

A Somogyi rebound is not always triggered. Whether it happens at all, how low the blood glucose must go, or how fast the blood glucose must fall to trigger a rebound is individual to each animal. The bg does not need to be dangerously low for a Somogyi rebound to be triggered. Rebounds can occur when the blood glucose is in "safe" levels, say around 120 mg/dL, but the bg is dropping very rapidly. For example, if the blood glucose drops very rapidly from the 400s to the low 100s in a relatively short time, the animal is never hypoglycemic (the blood glucose stayed above 100), but the body senses danger in the rapidly falling blood glucose, and the Somogyi rebound can be triggered.

When to suspect Somogyi rebound
If you are monitoring urine glucose, Somogyi rebound is suspected when the morning urine is persistently high. It can also be suspected when the morning urine glucose is high, the afternoon urine glucose is "negative" and the evening urine glucose is high.

Somogyi is also suspected when symptoms such as excessive urination, excessive drinking, symptoms of hypoglycemia, and weight loss continue, even as the insulin dose is increased. Before a rebound, the period of hypoglycemia may be short and you may not notice the symptoms of hypoglycemia. That's the point of the rebound - to avoid further hypoglycemia.

Somogyi can be diagnosed when you get blood glucose levels below 65mg/mL followed by hyperglycemia (typically >300 mg/dL) within one 24-hour period after an insulin injection.

During the course of diabetes management, if you continue to see no improvement in your pet's condition even after increasing the insulin dose, please ask your vet about the possibility of Somogyi rebound. Also, if you are having difficulty getting your pet regulated or are getting very strange bg curve results, you might suspect Somogyi. It is not uncommon to go past the correct insulin dose and get into a rebound situation and many owners have found that their difficulty in achieving regulation is due to chronic insulin overdosing and rebounding.

Treatment
The treatment for Somogyi rebound is to DECREASE the insulin dose. Since the current insulin dose is too high and is causing a rebound hyperglycemia, treatment is to DECREASE the insulin dose to a level where the blood glucose will not drop so low. If the rebound is being triggered by blood glucose that is falling too rapidly, you may need to decrease the dose, change the feeding and injection timing, or try an insulin that has a more gradual onset.

Is Somogyi A Common Occurrence?
Many pet owners are told that Somogyi is a rare event, but that seems to be based on information from human diabetics. From talking with owners of diabetic pets, Somogyi rebound is not uncommon, and many pets have experienced Somogyi rebound. This makes sense because humans are able to test their bg frequently and they can sense the physical signs of their low bg and do something (eat) to prevent a severe hypo / rebound situation. Since we usually can't monitor our pets that closely and they can't tell us their bg is low, it is not uncommon for pets to get into Somogyi rebound situations.

Other terms
Because Somogyi can be caused by too much insulin or hypoglycemia, Somogyi rebound is also called insulin-induced hyperglycemia, or hypoglycemia-induced hyperglycemia. Somogyi is the last name of the researcher who identified this phenomenon.

This is one of the more complicated issues when caring for a diabetic pet. Please discuss Somogyi rebound with your vet. Your vet will be able to explain it to you and determine if your pet is experiencing a rebound.

	Somogyi Rebound