Adrenal gland tumors are common in ferrets over 4 years old. The normal adrenal gland contains several types of cells that produce different hormones, such as cortisone and some male and female hormones. Excessive amounts of female hormones are often produced by adrenal gland tumors. There are no blood tests that absolutely prove that a ferret has an adrenal gland tumor, because the hormones and their effects are so variable. Palpation, radiography, and ultrasonography are used to identify an enlarged adrenal gland. The enlargement may be caused by hyperplasia (normal cells proliferating at an unusual rate), or by a benign or malignant tumor.

Possible cause of adrenal gland tumors

Early spaying or neutering. It has been suggested that spaying and neutering 6- to 7-week-old ferrets induces adrenal gland tumors. 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.

Individual people and animals are more susceptible to some types of cancer than others. 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. Early spaying or neutering is certainly not the whole answer, and may not even be part of the answer. 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.

Extended photoperiod. 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. By definition, tumor cells are out of control, and modifying photoperiod cannot reverse hair loss when any type of tumor is producing sex hormones.

People want their ferrets to be awake and playing in the evening when they come home from work, so the ferret is exposed to natural light all day, and artificial light in the evening. The obvious way to limit the ferret's exposure to 8 hours of light a day, without preventing him from interacting with his family, is to give him a dark place to sleep during the day. It has to be really dark, excluding all light, like a moonless night.

This might be arranged by putting the ferret's cage inside a well-ventilated closet, or using light-excluding drapes on the windows in the ferret's room. Reducing the ferret's exposure to light usually results in an improvement in coat condition and an increase in body weight a few weeks after the new arrangement - these responses show that the original photoperiod was too long. Providing short days only during the winter months is sufficient, as this mimics the natural seasonal variation in day length.

In a survey of about 300 ferrets performed in the Chicago area in the early '90's, the lowest incidence of adrenal gland tumors was found in ferrets used for breeding, and these animals must have been housed under short photoperiod at least part of the year or they would not have been productive. The association between adrenal gland tumors and artificial light conditions cannot be ignored.

Even if there is also some association with removal of gonads, the risk of not spaying is far greater than the chance that a spayed jill will develop adrenal tumors at a young age. About 50% of unspayed jills left in heat too long will develop bone marrow hypoplasia and die, but under natural light conditions, a very small percentage of ferrets spayed at any age develop adrenal tumors. Modifying your home to provide a more natural photoperiod in the winter is a simple thing compared to any of the alternatives once a ferret is diagnosed with an adrenal gland tumor.

Signs that a ferret has an adrenal tumor

Sometimes weight loss, hair loss, and itching for no apparent reason, are the only early signs of adrenal cancer in either a male or female ferret. Intact hobs with adrenal tumors might have permanently enlarged testicles but will be sterile. The first sign noticed by the owner of a spayed female with an adrenal gland tumor is often the sudden appearance of a swollen vulva, as if she were in heat.

Causes of hyperestrogenism in jills

There are two common reasons for jills coming in heat long after they have been spayed. A mistake made during the spay surgery is not one of them. A jill spayed incompletely as a kit comes in heat at 4 to 6 months old, depending on the hours of light each day, the same as if she were not spayed at all.

1. Ectopic ovarian tissue. Occasionally ovarian tissue grows at the site of the spay surgery, or elsewhere in the abdomen. It is not regrowth of an ovary, it is new tissue that functions like an ovarian follicle, producing estrogen. This may happen years after the spay, for unknown reasons. If the jill is left in heat a long time, she can suffer the same side effects as with a normal estrus, including loss of hair and suppression of bone marrow. Surgical removal of the abnormal tissue immediately ends the estrus and its side effects. Injectable hormones, that work well on normal jills in heat, do not always work on jills with ectopic ovarian tissue.

2. Adrenal gland tumors. Exploratory surgery may be necessary to distinguish jills with adrenal gland tumors from those with ectopic ovarian tissue. It is possible for a jill to have both problems at once.

Prognosis for ferrets with adrenal gland tumors

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. New techniques using cryosurgery have made removal of an adrenal gland a safer procedure, and most ferrets recover uneventfully.

Mitotane (Lysodren) is a drug that reduces the amount of hormone being produced by a benign inoperable tumor, extending the quality life time of the ferret. Other drugs used in humans are being tried in ferrets.

Some tumors are malignant and do not respond to Lysodren or other treatments. They metastasize to other organs or recur after removal. Ferrets with malignant tumors have a short life expectancy after diagnosis.