Page 332 - Problem-Based Feline Medicine

324 PART 6 CAT WITH WEIGHT LOSS OR CHRONIC ILLNESS

● Very rarely, spontaneous necrosis of the tumor can Clinical signs
result in temporary or permanent remission of clin-
Hyperadrenocorticism is typically seen in middle-aged
ical signs.
to older cats. Females may be over represented.
History is often vague, but usually includes polyuria,
Prognosis polydipsia, polyphagia, weight loss and lethargy,
and affected cats may have a history of recurrent infec-
The long-term prognosis is poor. However, because the tions and/or abscesses.
tumors grow very slowly, the short-term prognosis may
Since cortisol antagonizes insulin, approximately
be good to guarded with survival times of 4–48
80% of cases develop diabetes, which may or may not
or more months reported.
be insulin resistant, based on the insulin dose adminis-
tered.
Prevention Cats with hyperadrenocorticism typically have poor
coat condition, spontaneous alopecia, very fragile
Since acromegaly is usually caused by a slow growing thin skin that bruises easily and a pot-bellied
pituitary tumor, its development cannot be prevented. appearance. Hepatomegaly is often palpable.

Diagnosis
HYPERADRENOCORTICISM
Hyperadrenocorticism should be suspected in any cat
Classical signs with the clinical signs described above, particularly if it
has unstable diabetes, and/or a long history of exoge-
● A rare condition of middle-aged and older
nous corticosteroids administration.
cats.
● Poor coat condition and pot-bellied Since hyperadrenocorticism is frequently associated
appearance. with diabetes, serum biochemistry and urinalysis often
● Polyuric, polydipsic, polyphagic and often reveal persistent hyperglycemia, glucosuria ±
diabetic. ketonuria.
Unlike in dogs, a stress leukogram is rarely present,
although lymphopenia may be seen.
Pathogenesis
Increased liver enzymes and hypercholesterolemia
In cats, hyperadrenocorticism, more correctly termed may be seen regardless of whether or not the cat has
hypercortisolism, can be caused by: diabetes.
● Adrenocorticotropin (ACTH)-secreting pitu-
Making a diagnosis of hyperadrenocorticism can be
itary tumors;
very difficult:
– Approximately 80% of cats with hyperadreno-
● Few of the tests have well-established specificity
corticism have a pituitary tumor and most are
and sensitivity in cats.
microadenomas.
● It is usually necessary to use a combination of tests.
● Adrenal tumors that autonomously secretes cor-
tisol; In cats, the most useful screening tests are:
– Represent about 20% of cases, and approxi- ● Adrenocorticotropic hormone (ACTH) stimula-
mately 50% of adrenal tumors are benign ade- tion test – Collect baseline blood sample, give
noma, and 50% are malignant. 0.125 mg of synthetic ACTH IV, collect blood after
● Iatrogenic hyperadrenocorticism can be caused 1 ± 2 hours. Normal basal serum cortisol concen-
by giving long courses of exogenous corticos- tration is 10–110 nmol/L (0.36–3.6 μg/dl); at 1 h
teroids (parenteral, oral or topical) or megestrol and/or 2 h after ACTH is 210–330 nmol/L
actetate. (7.6–11.9 μg/dl); > 330 nmol/L (> 11.9 μg/dl) is