Affects: Cats, Dogs
Cushing's syndrome disease, also known as hyperadrenocorticism and spontaneous hypercortisolism, is a condition resulting from an endocrine disorder where too much adrenocorticotropic and cortisol hormones are produced, causing toxicity. It may arise in animals as well as in humans. Cushing's is an umbrella term for conditions caused by elevated cortisol and adrenocorticotropic hormone levels.
Cushing's disease most commonly refers to pituitary-dependent hyperadrenocorticism, the most common condition of Cushing's syndrome, but 'Cushing's' is used to refer to all hyperadrenocorticism conditions.
Cats are less likely to be diagnosed than dogs. Cushing's occurs infrequently in hamsters. It may be more common but due to hamsters not being routinely treated it may go undiagnosed.
Signs And Symptoms: Cushing's has a wide variety of symptoms and most gradually appear with a slow onset. The reason for the wide variety is due to how cortisol affects many different systems of the body.
Symptoms in dogs include:
Dermatological symptoms include:
Rare clinical signs of Cushings include:
A potbelly appearance is present in 90% of dogs with Cushing's, the cause is a hormonal redistribution of body fat and the breakdown of abdominal muscles. This breakdown of muscle protein leads to muscle weakness and lethargy.
Causes: Pituitary-dependent Cushing's is caused by production of too much adrenocorticotropic hormone by a functioning pituitary tumour. The tumour may be benign or malignant. Adrendal-dependent Cushing's is caused by a primary adrenal disorder.
Iatrogenic Cushing's is caused by long term use of corticosteroid-type medicine which can produce the same effects as cortisol produced by the body.
Risk Factors: Older dogs are more likely to present with Cushing's syndromes. Greater prevalence has been observed in some breeds such as the Yorkshire Terrier, Poodle (miniature), Miniature Dachshund, Boxer, Irish Setter, and Basset Hound. One study found bitches to be 1.4 times more likely to be diagnosed than dogs.
Diagnosis: The presentation of clinical signs occurs with great variation due to the gradual onset of Cushing's. In cases where a tumour is the cause it may take months or years for a diagnosis to occur. A study looking at 66 records of dogs with Cushing's found the duration of clinical signs before diagnosis to be between 1 and 36 months with a median of 8 months.
Routine diagnostic testing for Cushing's includes: a complete blood count, urinalysis, and a serum biochemistry panel; however the abnormalities these tests detect are not specific to Cushing's. Abnormalities that can be found in a complete blood count include: thrombocytosis, neutrophilia, lymphopenia, erythrocytosis, eosinopenia, and monocytosis. Abnormalities that can be found via serum biochemistry include: hyperglycaemia, hypercholesterolaemia, hypokalaemia, increased alkaline phosphatase concentration, alanine aminotransferase levels, creatinine concentration, lipase activity, and decreased urea concentration.
Ultrasonography, CT scans, and MRI are used to identify any abnormality in the pituitary or adrenal gland. This helps diagnose if the patient has pituitary-dependent Cushing's or adrenal-dependent Cushing's.
Treatment: Treatment of Cushing's depends on the cause. It is possible to cure Cushing's if the tumour is small, benign, and located on the adrenal gland; however, this is not common. Hypophysectomy is an option for patients with good clinical signs and a high life expectancy. Inoperable pituitary tumours may be treated with radiation, this is therapeutic as can take up to 16 months for change to show.
Prognosis: Prognosis varies based on the type of Cushing's, if the tumour is benign or malignant, and treatment method. Median survival times for dogs of 662-900 days have been observed in pituitary-dependent cases treated with trilostane, and 353-475 days for adrenal-dependent cases treated with trilostane. Survival rates of 72-79% have been observed in dogs with pituitary-dependent Cushing's four years after a hypophysectomy. Dogs affected by adrenal-dependent Cushing's that underwent an adrenalectomy had a median survival rate of 533-953 days.