Adrenal Gland Disease in Ferrets
Adrenal gland disease (AGD) in ferrets is one of the more common conditions that affects ferrets in North America. The signs are due to an abnormal production of sex steroids and androgrens but we do not know why the adrenal glands form tissue that causes this production. These steroids can lead to numerous disease conditions throughout the body. The average age that AGD occurs in ferrets is 3-4 years old. Adrenal gland disease may be more common in ferrets that have been spayed or neutered but since most pet ferrets are desexed, it is difficult to know if this statement is true.
Adrenal Glands
Ferrets, like most mammals, have two adrenal glands. Each gland is situated near the front edge of the corresponding kidney. Adrenal glands are small organs that secrete specific hormones to help the body maintain certain functions.
Signs
Signs of AGD in ferrets can include hair loss (referred to as alopecia) that typically starts on the tail and can include the entire rest of the body. About 30% of the ferrets with AGD are itchy. Most females have an enlarged vulva and some male ferrets have difficulty urinating due to an enlarged prostate gland. About 30% of ferrets with AGD will manifest some signs of sexual behavior such as aggressiveness towards other ferrets or animals.
These signs are all due to the increased concentration of sex steroids in the bloodstream.
Cause
AGD is characterized by visible enlargement of one or both adrenal glands. The cause of the enlargement can be benign or malignant but even if the cause is malignant, the cancerous adrenal gland cells rarely spread to other areas of the body. The underlying cause for the transformation of a normal adrenal gland into a diseased one is unknown. Theories on why this occurs includes genetics (e.g. inbreeding); spaying or neutering at an early age; or prolonged exposure to daylight (i.e. increased photoperiod). The studies necessary to determine the ultimate cause of AGD have not yet been done.
Diagnosis
A physical examination by your veterinarian coupled with typical signs is often enough to diagnose AGD. Hormonal blood testing can be used to confirm it but the disease is usually so obvious that it is typically unnecessary to run these tests for a firm diagnosis. Other lab work, such as a complete blood count (CBC) and plasma biochemistry, will help assess the general health of the ferret. Diagnostic imaging, such as radiographs and/or abdominal ultrasound, can be used to confirm the diagnosis, check for other disease conditions, and determine if one or both adrenal glands are diseased.
Treatment
It is possible to cure AGD with surgery. Adrenalectomy is a procedure that removes the diseased adrenal gland or or glands. In some cases, only part of a diseased adrenal gland is removed, such as when surgery is too difficult or risky for full removal. If signs continue after this type of surgery, medical therapy may also be needed. Most ferrets do well with surgery but the risks increase if the ferret has other diseases.
Medical therapy is another option but does not cure AGD. In the best possible case, medical therapy can limit or reverse the changes due to AGD. Medical therapy does not prevent the diseased glands from growing, and so over time it is likely that signs will recur. Medications that can be effective in ferrets includes those that have an effect on sex steroid release such as gonadotropin-releasing hormone (i.e. GnRH) agonists (e.g. leuprolide acetate or Lupron® and deslorelin acetate implants or Superlorin®); androgen receptor blockers (e.g. flutamide or Eulexin® and bicalutamide or Casodex®); and anti-androgen drugs (e.g. finasteride or anastrozole or Arimidex®). Some veterinarians are of the opinion that early treatment with GnRH agonists could prevent adrenal gland disease from developing, but evidence in the North American population of pet ferrets is lacking and the long-term effects are unknown at this time. Melatonin implants, which have an effect on photoperiod, may occasionally be helpful.
Some owners opt for no treatment. In some cases, the ferret may have an acceptable quality of life with AGD if the only sign might be hair loss. Once the ferret exhibits signs from AGD that negatively affect the quality of life, then most people agree that some action must be taken. Euthanasia should be considered when a good quality of life is no longer possible. This can occur when medication is no longer effective, when surgery is not an option, and if an owner feels the quality of life has suffered too much.
Prevention
Some researchers recommend not spaying or neutering ferrets but there is not enough evidence to prove this decreases the risk of a ferret developing AGD. Many owners object to the strong musky odor of intact male and female ferrets. Plus, intact female ferrets must be bred or medically taken out of heat or they will develop a fatal anemia associated with prolonged heat.
Adrenal Gland Disease in Other Animals
Adrenal gland disease that results in overproduction of hormones in other animals is often called hyperadrenocorticism or Cushing’s disease. While the disease seems similar to AGD in ferrets, the signs, cause, and treatments are significantly different.