Hyperadrenocorticism in dogs: treatments and life expectancy

Introduction

Hyperadrenocorticism (HAC) in dogs, also known as Cushing’s syndrome, is characterised by polyuria and polydipsia, polyphagia, bilateral alopecia, muscle atrophy with generalised weakness, hepatomegaly and lethargy, all of which affect both the patient’s and owner’s quality of life. HAC is also associated with life-threatening complications such as pulmonary thromboembolism, acute pancreatitis, hypertension, proteinuria, infectious diseases, diabetes and mucocele. 

Several questionnaires have been designed for veterinary surgeons and owners in order to establish a scale that helps evaluate this quality of life, optimises the disease’s management and increases survival. If the disease or its treatment has any negative impact for the owner, it could lead to treatment discontinuation or even euthanasia.^1,2

Hyperadrenocorticism: prognosis and treatment

The options for treating, monitoring and making a prognosis vary depending on the patient’s form of hyperadrenocorticism. Therefore, vets must differentiate between pituitary-dependent hyperadrenocorticism (PDH) and adrenal tumour hyperadrenocorticism (ATH) before selecting the most appropriate treatment.

The most popular pharmacological option for PDH is trilostane. The use of other drugs, such as mitotane or ketoconazole, has been reported in veterinary literature but with worse results. A hypophysectomy, i.e., surgical removal of the pituitary gland, is available at a few European centres as a viable option for small tumours.

The treatment of choice for ATH, on the other hand, is an adrenalectomy. However, surgery is often contraindicated for one of various reasons.In this case, the main medical options are the same as for PDH.

The current aim of the medical treatment of hyperadrenocorticism in dogs is to improve the clinical signs and therefore the patient’s quality of life, although it is not a curative approach. The type of therapy is normally selected based on the form of the HAC and the vet’s personal experience.¹

Cushing’s syndrome in dogs: life expectancy

There is a popular misconception that dogs with HAC have the same chance of survival regardless of whether their condition is treated. This sweeping statement could be true for some dogs, but almost certainly not for all. Survival depends on the clinical signs and complications associated with the disease.  Conversely, not all dogs that return positive HAC tests need treatment, rather this decision should be tailored to each patient. The treatment of HAC may uncover other diseases that were masked by the anti-inflammatory effects of hypercortisolaemia. For example, clinical signs of atopy or degenerative joint disease may develop during HAC treatment as cortisol levels decrease.^1,2

Dogs with hyperadrenocorticism have a life expectancy of approximately 36 months. It is important to note that treatment usually leads to a significant improvement in both the dog’s and owner’s quality of life. If the disease is treated in time, the patient’s life expectancy may be close to normal, and they may enjoy a quality of life that is acceptable to the owner.¹  

References

1. Schofield I, O’Neill DG, Brodbelt DC, et al. (2019). Development and evaluation of health-related quality-of-life tool for dogs with Cushing’s syndrome. J Vet Internal Med. 33: 2595-2604.

2. Behrend EN. (2015). Canine hyperadrenocorticism. En Feldman EC, Nelson RW, Reusch CE. (Eds).  Canine and Feline Endocrinology. 4th ed. Elsevier: 337-417.