Adrenal disease causes lesions or tumors on one or both adrenal glands. The adrenal glands—in ferrets as in humans—are complex organs (located near the kidneys) that produce certain sex hormones as well as secretions necessary for food metabolism, muscle maintenance, proper healing of wounds, and other important functions.

A benign glandular tumor is known as an adenoma; a malignant (cancerous) one is called a carcinoma. Fortunately, most adrenal tumors are benign. Unfortunately, even benign adrenal tumors cause problems for ferrets. In addition to losing their hair, adrenal ferrets lose muscle mass and have little energy. The most common symptom of adrenal disease is “alopecia,” or baldness, usually starting at the butt. Males may lose hair starting at the neck. In spayed females, the vulva can become swollen. Other common signs are increased itching and scratching, a potbelly, muscle wasting, orange skin patches, sexual aggressiveness (especially in males), and brittle fur. Sometimes you will also see a thinning of the skin, excessive drinking and urination, anemia, and weight loss. To make things especially confusing, not all these symptoms are present in every case. Baldness or a swollen vulva are sufficient cause for immediate treatment. But if you're not sure, you can have an ultrasound performed by an experienced technician to detect a mass on the adrenals. Ultrasound is not entirely reliable, however; for instance, it can't detect very tiny tumors. Another option for diagnosis is the ferret adrenal panel, available only at the University of Tennessee (also referred to simply as a Tennessee Panel). For this test, your veterinarian must draw blood, freeze it, and ship it under climate-controlled conditions to Tennessee. Then you have to wait for the results. Because of the expense involved with these two diagnostic tools, ultrasound and the adrenal panel should be used only for questionable cases.

There's lots of debate as to why adrenal disease is so common in American ferrets. One theory says that poor nutrition can lead to these tumors. Another blames inbreeding and a genetic pool that isn't very diverse. Some individual people and animals are more susceptible to some types of cancer than others. In theory, some ferret families may be especially susceptible to adrenal gland cancer. It is likely that more than one factor determines any ferret's susceptibility to adrenal gland abnormalities. It's also thought that the early-alter practice (in which ferrets are spayed or neutered at 5 or 6 weeks of age or earlier) is a source of later adrenal problems. The theory is that the adrenal glands of animals spayed or neutered very young might try to compensate for the lack of normal sex hormones by proliferation of cells that produce sex hormones. However, many ferrets spayed or neutered when much older have developed adrenal gland tumors, and occasionally animals that have not been spayed or neutered also have adrenal gland tumors. Early spaying or neutering is certainly not the whole answer. Finally, some people believe that artificial light cycles mess up the hormone cycle of ferrets, leading to adrenal problems. The disease was uncommon in the hunting ferrets that were their ancestors, and is still rare in animals that live outside, as they tend to do in the UK and in Australia. The incidence of adrenal gland problems is increasing in the UK as pet ferrets begin to share their owners' homes instead of living in the back garden. It is possible that the incidence of adrenal gland cancer has increased because we have forced our ferrets to adapt to our life style. Ferrets are strongly affected by photoperiod. Under natural conditions, there are only about 8 hours of strong light a day in the winter months, and the proportions of light and dark gradually change during the spring and fall. We have removed all these stimuli when we keep the ferret in a house where electric lights extend day length to at least 12 hours, all year round. Changing photoperiod causes the ferret to lose weight and hair in the spring, and come into breeding condition. In the fall, as the hours of light decrease, ferrets stop breeding, grow a heavy winter coat, and put on extra fat to prepare for the cold weather. A primitive part of the brain called the pineal gland mediates the ferret's response to light. The pineal gland produces a hormone called melatonin only during hours of darkness. Melatonin reduces the output of gonadotrophins from the pituitary gland. Gonadotrophins bind to cells in the ovary or testicle, inducing production of sex hormones. The same gonadotrophins also bind to cells in the adrenal gland. When ovaries and testicles are removed, these gonadotrophins can bind only to adrenal cortical cells.

It is possible that constant stimulation of the adrenal glands because of the long hours of light eventually causes first benign hyperplasia (enlargement), and then benign tumors to develop in the adrenal cortex. In some animals, the tumors become malignant or are malignant from the outset. Whether the condition is hypertrophy, a benign tumor, or cancer, excessive levels of adrenal cortical hormones are produced. Hyperplasia may be corrected if the ferret is put in a place where the light can be limited to 8 hours a day, and the ferret's hair starts to regrow 3 to 6 weeks after the change.

If left untreated, ferrets with adrenal gland tumors usually lose all but the hair on their heads and a tuft on the tail tip. Their skin gets very thin, they have a pot-bellied appearance, and they sleep most of the time. Fortunately, although they have an odd appearance with almost no fur on their bodies, ferrets with benign adrenal gland tumors can live a reasonably normal life, if they do not become anemic due to high levels of estrogen. Jills often appear to be in heat, and because this is associated with a swollen and open vulva, they are susceptible to urinary tract infections. Neutered or intact male ferrets may develop life-threatening urinary obstruction because high hormone levels cause the prostate gland to hypertrophy (enlarge) and constrict the neck of the bladder.

The most effective treatment is to surgically remove the abnormal adrenal gland. This is the only choice to relieve prostate hypertrophy, which it does within 48 hours. The adrenal glands produce many important substances required for life. If there are tumors on both glands, one can be removed, but part of the second one must remain, even if it means leaving part of the tumor there, too. For some undetermined reason, the left adrenal gland is affected more often than the right. This is a great source of relief to vets, because removal of the left adrenal gland is not an excessively difficult surgery and has a low risk of complication. Because the right adrenal is located near several large blood vessels, it can be difficult or even impossible to remove. New techniques using cryosurgery have made removal of an adrenal gland a safer procedure, and most ferrets recover uneventfully.

If the ferret is very old or in poor health, surgery may not be an option. Also, a ferret who has already had one adrenal gland removed might still be suffering from adrenal disease. For these ferrets, the problem can often be controlled (but not cured) with medication. One option is Lysodren (mitotane), which must be given orally every three or four days without fail for the remainder of the ferret's life. Another option is the drug Lupron, given in monthly injections by a vet. (Stronger, twice yearly Lupron injections are another, but more expensive, option.) Whether your vet recommends Lysodren or Lupron depends on the ferret and the situation. The drugs work in different ways. If the ferret is younger and you are on a budget, a vet may try Lysodren first (it's not cheap, but it's cheaper than Lupron). But some ferrets don't respond well to Lysodren and experience nausea or no results. Also, Lysodren lowers the blood glucose level, so it would cause serious problems in a ferret who already has insulinoma (a blood-sugar regulation problem). Lupron is also recommended if a ferret's owners are not up to the medication regimen required with Lysodren.

Some owners don't wish to put their ferrets through the stress of surgery or are unable to spend the money. But drug treatments—aside from being less effective and having side effects—are just as expensive as surgery in the long run. Adrenal ferrets who do not undergo surgery sometimes regrow their hair, but this does not mean the adrenal tumor has gone away. Adrenal disease is cumulative and progressive. And although the tumors don't appear to be painful, the other problems associated with this disease greatly decrease the quality of a ferret's life. Without surgery, your ferret can live bald and relatively happy for six months to two years; with surgery, they can live a full life span (eight years on the average) with good health. Ferrets up to 6 years old are considered good candidates for surgery, and recovery time is quick (all of my ferrets have recovered within two weeks). Also, during exploratory surgery the vet can look for other common diseases such as insulinoma, spleen problems, or cysts.