ThinkstockWhile there are a vast amount of possibilities for why a ferret, may be lethargic, an excess of insulin is often the culprit.

Today, as we steal from the old “Perry Mason” TV show, we are going to discuss the “Case of the Tired Ferret.” (Yes, I know I am dating myself with that reference.)

Sneaky (great name for a ferret!) is a 3-year-old ferret who recently has been spending more time than usual sleeping. He does have moments of activity and still seems to be eating well, but his naps have grown longer and longer and his play time is correspondingly greatly reduced. Ferrets do spend quite a bit of time sleeping; however, during their awake time, they’re going virtually nonstop. Wild ferrets use this nonstop awake time hunting, while captive ferrets spend this awake time getting into mischief. Sneaky is definitely having a problem.

Sneaky’s apparent lack of energy could reflect any number of potential disease processes, and we do not have the room to discuss all of them. In fact, I probably cannot even think of all of them, but I can share with you the most common possible cause for Sneaky’s symptoms.

Ferrets have a propensity to develop a disease called insulinoma. This disease occurs when one or more tumors (insulinomas) develop in a ferret’s pancreas. These tumors produce insulin in excess of what is needed for normal blood sugar maintenance, and this excess insulin causes a reduction in blood sugar directly proportional to the amount of excess insulin.

Insulin, as I mentioned, is produced by the pancreas and is used in the body to bring sugar (glucose) from the bloodstream into the cells of the body to be used as an energy source. It is a beautifully balanced system designed to maintain an appropriate blood sugar level while providing the body’s cells with the fuel they need to work. When insulin levels rise unchecked, as is the case with insulinoma, the blood sugar level drops. This will cause weakness and excessive sleeping initially as demonstrated by Sneaky, but as the process progresses, the blood sugar can drop so low as to cause seizures. This is the body’s attempt to “shake loose” stored glucose from the muscles as they spasmodically contract during a seizure in order to fuel the body. Further progression of the condition results ultimately in death.

Insulinoma in ferrets can occur as one or a few nodular masses within the pancreas or many often-microscopic masses throughout the pancreas. Diagnosis is relatively simple, requiring a blood sample to measure, among other things, blood sugar level and insulin level. If the insulin level is too high relative to the blood sugar level, we have a diagnosis of insulinoma. We do not, however, know which form we are dealing with. Personally, I like to use ultrasound imaging of the pancreas in a ferret with insulinoma to try to determine if there are but one or a few nodules within. If that is the case, a relatively straightforward surgical procedure can be performed to remove the nodules.

If it is more likely that there are many tiny nodules throughout the pancreas, there are a couple of options for treatment. One is a surgical procedure to remove a large portion of the pancreas, thus eliminating a significant number of the tiny insulinomas and hopefully resolving the excess insulin production as a result. This can be very successful, but there are cases that even with removal of 90 percent of the pancreas, insulin levels remain too high. These cases require medical therapy to counteract the excess insulin. Unfortunately, this therapy is not curative and is therefore lifelong. It does, however, usually afford control of the disease allowing the ferret to live a more normal active life.