What are symptoms for Cushing’s disease in dogs?
Symptoms for Cushing’s disease in dogs are variable and confusing with other common diseases. This article will cover the causes of Cushing’s disease in dogs, diagnosis and treatment. Cushing disease is a common multisystemic endocrine disorder of dogs, also called Hyperadrenocorticism.
In Cushing disease, a dog’s body starts making too much of a hormone, Cortisol from adrenal glands. Adrenal glands are two small glands located near both kidneys. In healthy pets, adrenal glands produce a normal amount of cortisol which plays an important role in pet’s body’s internal functioning like stress management, weight control, etc. Too much or too low of cortisol may be life-threatening.
What causes Cushing’s disease in dogs?
Causes of Cushing’s disease are divided into three types based on what part of the body is involved or affected.
- Pituitary Gland Tumor Cushing’s disease
- Adrenal Gland Tumor Cushing’s disease
- Iatrogenic Cushing’s disease
The pituitary gland tumour is the most common cause of Cushing’s disease in dogs. Pituitary gland tumour is a mostly benign tumour in the brain and it counts for 85-90 % of total naturally occurring Cushing’s disease. Treatment of this type of Cushing’s disease is favourable and the prognosis is guarded. Malignant Pituitary gland tumours are quite rare in dogs.
All these tumours cause Pituitary gland tumour to make too much of a hormone, ACTH which acts on the adrenal gland to produce more cortisol.
Adrenal gland tumour causes 10-15 % of naturally occurring Cushing’s disease in dogs. The tumour can be benign ( adenoma) or malignant(carcinoma).
Iatrogenic Cushing’s disease is caused when steroids are given externally by mouth, a local application like skin ointments or ear drops or injection for a long time.
Irrespective of the cause of Cushing,s disease, symptoms for Cushing’s disease in dogs are almost the same.
What dog breeds are prone to Cushing’s disease?
Cushing is a middle-aged to old dog disease it is rare under one year of age. some breeds are more prone to Cushing’s disease in dogs like
- Boston Terrier
- Yorkshire Terrier
What are the symptoms for Cushing’s disease in dogs?
You may notice some or all of the following symptoms in your dog:
- Increase in appetite
- Increase in thirst
- Pants a lot
- Thin skin
- Weight gain
- Increase in urination
- Poor skin condition
- Hair loss
- General weakness
- Muscle weakness
- Recurring skin infections
- Urinary tract infection
- Neurological signs like ataxia, seizure, blindness, circling etc.
How do you test for Cushing’s disease in dogs?
Diagnosis is quite challenging at an early stage. It needs some common and special blood tests. Special tests include the LDDS test, ACTH stimulation test, HDDS test. Your veterinarian may follow some common steps in Diagnosis:
- A thorough history to rule out other common diseases of similar types
- Physical examination plays a very important role in reaching any conclusion
- Complete blood count (CBC) is a type of blood test. Your veterinarian may see high Eosinophils, low Lymphocytes, high Leukocytes (WBC) in the blood
- On blood chemistry test, we may see high ALP, ALT, cholesterol, and high blood glucose
- Urinalysis is a urine test we may see low urine specific gravity, protein in the urine (proteinuria)
- Special urine test, Urine cortisol: creatinine ratio is some times used as a screening test.
- Abdominal x-rays or ultrasound is used to see any growth or asymmetry of adrenal glands. In general, bilateral hyperplasia is seen with a pituitary gland tumour. Atrophy of one adrenal gland and enlargement of another adrenal gland is a common finding in adrenal gland tumour Cushing disease.
Your veterinarian will run some special tests for the Diagnosis of Cushing’s disease in dogs.
Low Dose of Dexamethasone suppression test (LDDS): In healthy dogs, injection of dexamethasone suppresses ACTH secretion from the pituitary gland, which results in a decrease in cortisol level in the blood. But a dog with Cushing’s disease resists to negative feedback mechanism of dexamethasone for ACTH suppression, which results in an increase in blood cortisol level at 4 and 8-hour post dexamethasone infection.
Dexamethasone is given @ 0.01 mg/kg IV by injection to the patient and the blood samples are collected at 4 and 8 hours post dexamethasone infection to measure cortisol level in the blood.
ACTH stimulation test: it is the best and cheap initial diagnostic test. It checks how well adrenal glands respond to externally injected ACTH. Synthetic ACTH is given @ 0.25 mg per Dog IV or IM. Blood samples are collected at different times and cortisol levels are measured in the blood. Both LDDS and ACTH tests are used to confirm Cushing disease. But they cannot differentiate causes of Cushing disease. For this, a High Dose of the Dexamethasone suppression test (HDDS) test is done.
What is the best treatment for Cushing’s disease in dogs?
The treatment plan depends upon the type of Cushing’s disease in dogs and Symptoms for Cushing’s disease in dogs. If it is adrenal gland tumour Cushing’s disease, then surgery is preferred to remove the gland. it will cure your pet of the problem. The success rate is quite good if the tumour has not spread to other body parts yet. Treatment and prognosis depend upon the cause of the Cushing’s disease.
- Dogs with Pituitary gland tumours can live a good quality of life for years with life long medications. In some cases, neurological signs can appear. If the Pituitary gland tumour grows bigger and starting to affecting the brain, then the prognosis is less favourable.
- Common medications used for Cushing’s disease are Mitotane or Trilostane. They can be used for both pituitary and adrenal gland tumour Cushing’s disease. Mitotane is an old drug with many side effects like vomiting, diarrhea, anorexia, weakness and lethargy. So, Mitotane is used less these days. Trilostane comes with lesser side effects, but it is more costly.
- Surgery is the best treatment of choice for adrenal gland tumours. Prognosis is good if the tumour is benign. But the prognosis is less favourable if adrenal gland tumour is malignant.
What is the life expectancy of a dog with Cushing’s disease?
Again, it depends upon the cause of the disease, in the pituitary gland tumour, life expectancy is 1.5 to 2 years. In the malignant adrenal gland tumour, life expectancy is only a few months. In benign adrenal gland tumour, the dog can live formal life if the tumour is removed surgically.
Follow up is very important in Cushing’s disease. Regular blood tests like CBC, blood chemistry and ACTH stimulation tests are done at 1, 3, and 6 months of an interval of the treatment. These tests help us to see any side effects of the drug and adjustment in the dose of the medication.
Some other important articles:
This information is NOT intended as a substitute for veterinary consultation for any of your pet’s diseases. Always consult your veterinarian for a diagnosis and treatment plan.
- Blackwell’s Five-Minute Veterinary Consult: Canine and Feline by Larry P. Tilley, Francis W. K. Smith
- Saunders Manual of Small Animal Practice by Robert G. Sherding and Stephen J. Birchard
- Emergency Procedures for the Small Animal Veterinarian by Signe J. Plunkett
- Merck Veterinary Manual by Susan Aiello
- 100 Top Consultations in Small Animal General Practice by Peter Hill, Sheena Warman, Geoff Shawcross
- Plumb’s Veterinary Drug Handbook by Donald C. Plumb
- Veterinary Emergency and Critical Care Manual, 3rd Edition by Karol A. Mathews
- Veterinary Guide for Animal Owners, 2nd Edition by C.E. Spaulding, D.M.V. Jackie Clay
- Small Animal Emergency and Critical Care for Veterinary Technicians Third edition by Andrea M. Battaglia, LVT, Andrea M. Steele, MSc, RVT, VTS (ECC)