HYPER ADRENOCORTICISM

Causes

• Cortisol is produced by the adrenal glands, and it is essential for regulating processes such as metabolism, stress response and immune function. 

• A dog’s body has two adrenal glands, each located near a kidney, and each adrenal gland has two main parts: Cortex: produces cortisol and Medulla: produces adrenaline  

• There are two common forms of this disease: 

  • Pituitary-dependent (80-85% of all cases) 

    • A small, benign tumor (adenoma) of the pituitary gland in the brain starts producing an excess of the hormone ACTH, which then stimulates the adrenal glands and makes them produce an excess of cortisol.  

    • Bichon Frise, Border Terrier, Jack Russell Terrier, Lhasa Apso, Miniature Schnauzer, Staffordshire Terrier (American/Bull), Yorkshire Terrier, Miniature Poodles, Dachshunds - Smaller Breeds

  • Adrenal-dependent (10-15 % of all cases)

    • A tumor of one or both adrenal glands, resulting in excess cortisol production  ​

    • Staffordshire Terrier (American/Bull) and German Shepherd  - Bigger Breeds

  • A third form results from administering cortisol as a medication, and this type is known as Iatrogenic Cushing’s syndrome.  

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Symptoms and Types

• In dogs, the most common clinical signs include-

  • polyuria/polydipsia,

  • polyphagia,

  • a pendulous abdomen,

  • panting,

  • muscle wasting, and

  • dermatological changes, including

    • alopecia,

    • pyoderma, and

    • thin skin ​

• Associated medical conditions ​-

  • Urinary tract infections 

  • Skin infections 

  • Neurologic problems, such as seizures and circling  

  • Blood clots (thromboembolic disease) 

  • Sudden blindness 

  • Gall bladder disease (mucocele) 

  • Diabetes mellitus 

Diagnosis

• Complete blood count (CBC) to look at blood cells 

• Chemistry panel to assess organ health 

• Urinalysis to assess kidney function and screen for urinary tract infection 

• More advanced testing may include the following: 

  • Chest X-rays if your dog is experiencing breathing issues and to screen for cancer 

  • Abdominal ultrasound to assess adrenal gland size and shape, examine the rest of the abdominal organs (e.g. liver, gall bladder) and check for other tumors 

  • Blood pressure measurement 

  • Urine culture and sensitivity (to confirm a urinary tract infection) 

• Specific adrenal gland function testing (multiple tests may be necessary): 

  • Low Dose Dexamethasone Suppression Test (LDDST)  

    • Preferred screening test for Cushing’s syndrome (in most cases)  

  • High Dose Dexamethasone Suppression Test (HDDST)  

    • Used to help distinguish between the two most common forms the pituitary and the adrenal dependent crushing's.

  • Other screening tests:  

    • ACTH Stimulation Test 

    • Urine Cortisol: Creatinine Ratio (UCCR)  

    • Measurement of blood ACTH level 

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Treatment

• Pituitary-dependent treatments 

  • Trilostane (trade name: Vetoryl)  

    • FDA-approved oral medication  

    • Decreases production of cortisol 

    • Possible side effects include decreased appetite, vomiting, diarrhea, lethargy, adrenal gland destruction and death 

    • Requires diligent monitoring  

  • Mitotane  

    • “Off-label” oral medication  

    • Destroys adrenal cells that produce cortisol; potentially reversible 

    • Possible side effects include decreased appetite, vomiting, diarrhea, weakness, irreversible destruction and death 

    • Requires diligent monitoring  

  • Selegilene (trade name: Anipryl)  

    • Questionable efficacy  

    • No longer recommended  

  • Radiation therapy of the pituitary tumor   

    • Has been used successfully with larger tumors (macroadenomas) 

    • Expensive 

    • Limited availability  

  • Surgical removal of the pituitary tumor  

    • Has been performed successfully 

    • Expensive 

    • Limited availability 

    • Possible complications 

• Adrenal-dependent treatments 

  • Surgical removal of the adrenal tumor (adrenalectomy)  

    • Preferred treatment whenever possible 

    • Complicated procedure, requires close monitoring after the operation  

    • Potentially serious complications (e.g. hemorrhage, death) 

    • Smaller tumors have better outcomes  

  • Medical therapy  

    • Prior to surgery to improve the patient’s condition 

    • Used when surgery is not an option  

    • Can improve clinical signs but the tumor remains unchanged 

  • Trilostane 

  • Mitotane 

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References

• Bugbee A, Rucinsky R, Cazabon S, et al. 2023 AAHA selected endocrinopathies of dogs and cats guidelines. J Am Anim Hosp Assoc. 2023;59(3):113-135. doi:10.5326/JAAHA-MS-7368

• Behrend EN, Kooistra HS, Nelson R, Reusch CE, Scott-Moncrieff JC. Diagnosis of spontaneous canine hyperadrenocorticism: 2012 ACVIM consensus statement (small animal). J Vet Intern Med. 2013;27(6):1292-1304. doi:10.1111/jvim.12192

• Behrend, EN. Canine hyperadrenocorticism. In Feldman EC, Nelson RW, Reusch C, Scott-Moncrieff, JCR. Canine & Feline Endocrinology. 4th ed. Elsevier Saunders; 2015:377-451.

• Also see pet health content regarding Cushing syndrome in dogs and cats.

• https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information/cushings-syndrome

• https://www.msdvetmanual.com/endocrine-system/the-adrenal-glands/cushing-syndrome-hyperadrenocorticism-in-animals#Key-Points_v92006896

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