Dogs With Cushing's Disease
Cushing's Disease ( Cushing's Syndrome), named after
a Boston surgeon who first described the disease in people, is caused
by elevated concentrations of circulating cortisol. It usually occurs in middle aged to older dogs, however, exceptions may
occur. Normally, the pituitary gland produces a
hormone, adrenocorticotropic hormone
( ACTH), which in turn stimulates the
adrenal gland to produce cortisol, a glucocorticoid. But if things get out of whack in either the
too much cortisol may be produced causing
Spontaneous (80-85% of cases)-the
adrenal cortex (outer part of
adrenal gland) produces excess cortisol
( corticosteroid) due to a small tumor on the
pituitary gland gland which causes the excess
production of ACTH. This is also called Pituitary Dependent Hyperadrenocorticism (PDH). Adrenal adenoma or carcinoma (15-20 % of cases)-tumor of the
adrenal gland. Approximately one half are
malignant. This type is more common in female dogs. Iatrogenic-excessive administration of glucocorticoids (steroids)
Signs and symptoms:
These will vary greatly depending on the amount of excess
cortisol and the length of the illness.
increased water consumption (polydipsia)
increased urination (polyuria)
hair loss--usually symmetrical and on the trunk
thinning of the skin
muscle weakness and wasting
facial nerve palsy
hyperpigmentation or depigmentation
wounds healing slowly
Definitive testing to differentiate Pituitary Dependent from Adrenal Tumor Hyperadrenocorticism
High-Dose Dexamethasone Suppression Test (HDDST)
Lack of suppression-- Cortisol production is not suppressed and levels remain above 1.5 ug/dl is diagnostic for
an adrenal tumor.
Suppression--If any cortisol value during the 8 hr testing falls below 1.5 ug/dl. This is consistent with PDH in
75% of dogs tested.
Plasma ACTH Concentration
Normal to high--PDH
Low- adrenal tumor
CRH Rsponse Test
No change in plasma
level- adrenal tumor
Surgery: Not an option for pituitary tumors, but is a possibility for
adrenocortico adenoma and small carcinoma if the dog is in otherwise good health and the
tumor is benign.
Malignant adrenal tumors that have already spread are poor
surgical risks and medical management may be preferred. For pituitary tumors, radiation therapy has been used with
success when the tumor is less than 15 mm in diameter. However, the radiation therapy will not be available at all
Medical management of Cushing's due to adrenal tumors uses a higher dose Lysodren than what is administered for
PDH. The higher dosage usually causes more side effects.
Medical treatment of PDH: For a more complete description of Cushing's Disease treatments/options, please see the
Informational Website on the Mar Vista Animal Medical Center site.
Lysodren (Mitotane or o,p’-DDD),
Anipryl ( L-Deprenyl, Eldepryl or Selegiline)
Tilley, LP, Smith, FWK,
The 5 Minute Veterinary Consult, Canine and Feline. 1997, Williams & Wilkins.
Mordecai Siegal (Ed.)
The UC Davis Book of Dogs. 1995, HarperCollins Publishers. Bonagura, JD (ed.)
Kirk's Current Veterinary Therapy XIII Small Animal Practice.
2000,W. B Saunders Company.