Adrenal Disease in Ferrets
Heidi L. Hoefer, DVM, ABVP
The adrenal glands are small organs, about the size of a lentil, and are located
in the abdomen. There are two glands, one on either side near the kidneys. Theadrenal glands are a very important source of hormone production in the body of allmammals, including people and ferrets. There is a common condition in ferretswhere the adrenal gland becomes abnormally large and begins to produce certainhormones at an excessive rate. Several hormones may be involved, particularly thesex hormones like estrogen and testosterone. Called "hyperadrenalcorticism" or justadrenal gland disease, this is a common ailment in middle-aged and older ferrets.
Adrenal disease usually occurs in ferrets over 3 years of age but can
sometimes be seen in younger ferrets. Clinical signs include varying degrees of furloss, often combined with itchy skin. The fur loss may begin as a subtle thinning ofthe coat, usually on or near the tail. In time, this fur loss progresses down the backand sides until the ferret becomes noticably "bald". Some spayed females willdevelop a swollen vulva very similar to the normal non-spayed female in heat (effectsof estrogens. Neutered male ferrets can become aggressive and behave like intactmales (effects of testosterone). Owners may report a stronger than usual odor inboth sexes. Some ferrets have trouble urinating (see below). In some long-standingcases, bone marrow suppression can occur and result in anemia and low plateletcounts. These ferrets bruise readily and may develop small red blood spots in theskin. These cases require immediate and aggressive veterinary therapy.
Fortunately, this is uncommon.
Diagnosis is based on clinical signs, palpation of adrenal glands, sonogram (or
"ultrasound") of the glands, and ultimately, surgical biopsy of the gland. Routineblood tests cannot diagnose the disease but are recommended to monitor the healthof other organ systems. Blood hormone levels are commercially available (at theUniversity of Tennessee Veterinary School) but this is an expensive test and cantake 4 weeks for results. Abdominal sonograms can be performed by anexperienced ferret ultrasonographer and for the money (about $175-200), may bethe best pre-surgical assessment of the adrenal glands, as well as other organs inthe abdomen.
Surgical Therapy for Adrenal Disease
Surgical treatment involves removal of the affected gland. This can be difficult
depending on which gland is involved. The left-sided gland is the easier one toremove and is the gland most often affected. The right gland is adhered to the venacava, the largest vein in the body. Surgery of this gland can be tricky and anexperienced ferret surgeon is recommended. In a small number of cases, bothglands may be affected. Removal of one gland and biopsy of the second or removalof both glands is recommended in these cases. Some of these glands arecancerous but metastasis (spread to other organs) is rare and prognosis is goodwith surgical removal. Most ferrets are disease-free following surgical removal of theaffected gland.
There may be other surgical conditions affecting the ferret with adrenal
disease, like pancreatic tumors (insulinoma), or hairballs in the stomach (from allthat itchy skin). Abdominal surgery in these ferrets can often correct and/ordiagnose multiple conditions and greatly improve the quality of life.
Medical Therapy for Adrenal Disease
Traditional medical therapy for hyperadrenalcorticism in other species
(Lysodren and ketoconazole) has variable effects and is not considered effective.
New hormonal therapies for adrenal disease in ferrets are currently beingresearched. Experimental treatment with the human drug leuprolide (Lupron®) isunderway. Lupron decreases levels of testosterone and estrogens. Lupron comes aspowder that needs to be reconstituted. It comes as a 1-month or 4 month depotinjection. The 4-month injection may alleviate clinical signs as long as 7 months. Theone-month drug usually needs to be administered every 1-2 months. These drugsare very expensive, e.g., wholesale cost of the 4 month ferret shot is about $200 (it'sabout $2000 for the human dose!)
Other experimental drug therapies include Arimidex® and Casodex®. Arimidex
blocks testosterone conversion into estrogen. Casodex® inhibits testosterone andmay be useful for those male ferrets that are straining to urinate.
Hormonal treatment of adrenal disease only alleviates clinical signs. It appears
that these drugs have no obvious effect on the tumor size or growth. Surgicalexcision is still the treatment of choice but in some cases where surgery is not anoption, "informed-consent" use of these drugs may be indicated.
Adrenal Disease and Urinating Difficulty
This is a well-recognized "syndrome" seen in neutered ferrets with
hyperadrenalcorticism. A cyst-like structure can develop around the urethra at theas it empties the bladder and results in inflammation, infection, straining to urinate(and defecate), and sometimes complete urinary obstruction. Some of these ferretsdevelop urinary tract problems before losing hair. It is thought that theoverproduction of adrenal androgens (male hormones like testosterone) stimulatesgrowth and cyst formation of the normally very small ferret prostate. Thisenlargement results in urine outflow obstruction. Although this is seen mostly in maleferrets, we have occasionally diagnosed this in spayed females. Although femalesdo not have a prostate, there may be some reproductive tract remnant in the samelocation as the male prostate and with excessive hormones, the effect is similar.
Diagnosis is based on clinical signs, palpation, radiographs, or ultrasound.
Ultrasound may be the best diagnostic test to image the cysts. Ferrets withcompletely blocked urinary bladders are emergencies; urine from the kidneyscontinues to fill the bladder and ultimately the bladder will rupture if the obstruction isnot relieved. Tiny urinary catheters (tubes) are placed into the bladder to try toempty it but this is a temporary measure. Correction is surgical; the affected adrenalgland must be removed and the cysts are suctioned empty with a needle orremoved. Often the cystic structures will recede once the hormone levels arereduced. Lupron may temporarily reduce hormone levels and allow urine to floweasier.
No one really knows the cause of adrenal disease in ferrets, but there are
some speculations and theories as to why this is so common. Very early neuteringis thought to play a role; most pet ferrets in the U.S. are neutered before 6 weeks ofage and maybe at a time when the adrenal glands are still developing. Disruption ofthe adrenal gland-pituitary-genital feedback mechanisms at such a young age maybe significant. The role of in-breeding and genetics has yet to be explored.
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