Cushing’s syndrome: identifying signs and supporting patients

• This article from VN Times(September/October 2026) can count towards your CPD – 25 minutes

Cushing’s disease, also called canine Cushing’s syndrome or hyperadrenocorticism, is a common endocrine disorder that affects middle-aged and older dogs (Kleszynski, 2024).

Although the condition can also occur in cats, it is considered rare; therefore, this article will focus on canine Cushing’s syndrome.

The condition develops when excessive amounts of the steroid hormone cortisol are produced. This may occur naturally as a result of a pituitary or adrenal tumour, or iatrogenically following prolonged administration of corticosteroid medications.

A UK study of more than 905,000 dogs estimated that approximately 1 in every 600 dogs receiving veterinary care were affected by Cushing’s disease over a one-year period (Schofield et al, 2021). As the clinical signs often develop gradually, they are frequently mistaken for normal ageing, delaying recognition and diagnosis.

This article explores the common clinical signs associated with Cushing’s disease, diagnostic considerations, current treatment options and the vital role of the veterinary team in supporting both patients and their owners throughout the diagnostic process and long-term management.

What is Cushing’s disease?

Cushing’s disease develops as a result of chronically elevated cortisol concentrations (PDSA, no date). Cortisol is the predominant glucocorticoid produced by the adrenal glands, playing a central role in regulating metabolic and physiological responses (Mârza et al, 2024).

Cushing’s disease can be classified as either naturally occurring or iatrogenic.

Iatrogenic

Iatrogenic Cushing’s is caused by excessive corticosteroid administration and should respond to gradual tapering of steroid medications (Koytzoumis, 2024).

Pituitary-dependent hyperadrenocorticism

Pituitary-dependent hyperadrenocorticism (PDH) is the most common form of Cushing’s disease, accounting for approximately 80% to 85% of naturally occurring cases (Dechra, 2026). It is usually caused by a small, benign pituitary adenoma that secretes excessive amounts of adrenocorticotropic hormone (ACTH).

The increased ACTH stimulation causes both adrenal glands to enlarge (bilateral adrenocortical hyperplasia) and produce excessive amounts of cortisol (Koytzoumis, 2024).

Adrenal-dependent hyperadrenocorticism

Adrenal-dependent hyperadrenocorticism (ADH) is less common, accounting for approximately 15% to 20% of naturally occurring cases (Sanders, Kooistra and Galac, 2018).

It develops when a functional tumour of the adrenal gland produces cortisol independently of pituitary control (Koytzoumis, 2024). These tumours may be either adenomas or adenocarcinomas (Greco, 2024).

Epidemiology of Cushing’s disease

Several factors have been associated with an increased risk of developing Cushing’s disease, including age, breed and body size.

Cushing’s disease most commonly affects middle-aged to older dogs, with the majority of cases diagnosed between 7 and 12 years of age. While any breed can develop the condition, several breeds appear to be predisposed, including miniature poodles, dachshunds, boxers, Boston terriers, Yorkshire terriers, American Staffordshire terriers and Staffordshire bull terriers.

PDH is more commonly diagnosed in smaller breed dogs. In contrast, ADH is more frequently reported in medium to large breeds of dogs, with affected dogs typically having a median bodyweight of 18kg to 20kg (Greco, 2024).

Common symptoms of Cushing’s disease

The clinical signs of Cushing’s disease often develop gradually and may be mistaken for the normal ageing process, which can delay diagnosis.

While the severity and combination of signs vary between patients, the most recognised clinical signs include:

• Polyuria and polydipsia, reported in approximately 95% of cases (Cook, 2019).
• Polyphagia.
• Abdominal enlargement (“pot-bellied” appearance).
• Skin and coat changes, including thinning of the skin, alopecia, scaling and poor coat quality.
• Calcinosis cutis.
• Poor wound healing.
• Hepatomegaly.
• Muscle wasting and weakness.
• Lethargy and reduced exercise tolerance.
• Reproductive changes, including anoestrus in females and testicular atrophy in males (Koytzoumis, 2024).

Some dogs may also present with concurrent conditions or complications, including poorly controlled diabetes mellitus, urinary incontinence, spontaneous thromboembolism secondary to hypercoagulability or lameness associated with ligament laxity and tearing (Koytzoumis, 2024).

Diagnosing Cushing’s disease

The diagnosis of Cushing’s disease is based on a combination of the patient’s history, clinical signs and diagnostic investigations. Routine haematology, serum biochemistry and urinalysis cannot confirm the diagnosis; however, they frequently reveal abnormalities that increase clinical suspicion and indicate the need for further testing.

Routine diagnostics

Haematological abnormalities typically reflect a stress leukogram, characterised by neutrophilia, lymphopenia, eosinopenia and monocytosis. Normal to high or mildly increased haematocrit and thrombocytosis may also be present (Cook, 2019). Serum biochemistry most consistently reveals a marked elevation in alkaline phosphatase activity, often accompanied by increased γ-glutamyl transferase activity. Hypercholesterolaemia and hypertriglyceridaemia are also common findings, while mild elevations in alanine aminotransferase, hyperphosphataemia, mild hyperglycaemia and reduced blood urea nitrogen may also be present (Cook, 2019).

Urinalysis commonly demonstrates dilute urine, with a urine specific gravity (USG) typically less than 1.020. In some cases, dogs may exhibit hyposthenuria (USG less than 1.008). Proteinuria is frequently identified and should be quantified using a urine protein-to-creatinine ratio. Urinary tract infections are also common due to the immunosuppressive effects of excess cortisol (Cook, 2019).

Further testing

Adrenocorticotropic hormone stimulation test. The adrenocorticotropic hormone (ACTH) stimulation test shows if the patient is overproducing cortisol by testing the response of the adrenal glands to stimulation by the hormone ACTH (Dechra, 2026).

The ACTH stimulation test involves measuring blood cortisol concentrations before and one hour after administration of a synthetic ACTH analogue to assess the adrenal glands’ ability to produce cortisol (Koytzoumis, 2024).

This test is not recommended for diagnosing naturally occurring Cushing’s disease, as it fails to identify approximately 20% of dogs with PDH and up to 40% of dogs with ADH (Koehler, 2024). However, ACTH stimulation tests can be useful for treatment monitoring, and it remains the preferred diagnostic test for iatrogenic Cushing’s disease. This is because plasma cortisol will not rise post-ACTH administration (Koytzoumis, 2024), as prolonged corticosteroid administration suppresses ACTH production, causing the adrenal glands to become atrophied. As a result, the adrenal glands produce little or no cortisol following administration of synthetic ACTH (Lathan, 2009).

Low-dose dexamethasone suppression test. The low-dose dexamethasone suppression test (LDDST) is the screening test of choice for canine hyperadrenocorticism. It’s a good screening test for hyperadrenocorticism when the dog has no concurrent medical conditions or when only dermatological abnormalities are observed (Greco, 2024).

The LDDST involves collecting a baseline blood sample to measure cortisol, followed by administration of a low dose of dexamethasone. Further blood samples are then collected 6 and 8 hours later (Cornell University College of Veterinary Medicine, no date).

The LDDST assesses the body’s ability to suppress cortisol production following administration of dexamethasone. In healthy dogs, dexamethasone suppresses ACTH release from the pituitary gland, resulting in a significant reduction in cortisol concentrations.

Dogs with Cushing’s disease fail to suppress cortisol production appropriately. In dogs with ADH, suppressing ACTH production has no significant impact on cortisol production. In dogs with PDH, the pituitary is desensitised to negative feedback, so a mild reduction in cortisol levels may be seen. If cortisol levels are suppressed by more than 50% at any point in a dog with Cushing’s syndrome, PDH is confirmed; however, the absence of significant suppression is not a reliable indicator of ADH (Koytzoumis, 2024).

High-dose dexamethasone suppression test. The high-dose dexamethasone suppression test (HDDST), combined with results from the LDDST or ACTH-response test, is used to differentiate between PDH and an adrenocortical tumour(s).

The HDDST is completed in the same way as the LDDST, just with a higher dose of dexamethasone administration (Cornell University College of Veterinary Medicine, no date).

Treatment

Most cases of Cushing’s disease can only be managed, not cured. The treatment approach for Cushing’s disease depends on the underlying cause, the patient’s clinical signs and the overall health status of the individual dog.

For most dogs with naturally occurring Cushing’s disease, medical management is the preferred approach.

Trilostane is currently the most used medication, it’s a steroid analogue that blocks a certain enzyme necessary for cortisol production, thus decreasing hormone level (Kleszynski, 2024).

Alternatively, mitotane can be used, although its use is less common. This is a chemotherapeutic medication that destroys part of the adrenal gland so that it can no longer produce cortisol (Kleszynski, 2024).

Surgical interventions, including hypophysectomy and adrenalectomy, may be considered in selected cases; however, these procedures are highly specialised, not widely available and carry significant risks. Similarly, radiotherapy may be an option for some dogs but access is limited to specialist referral centres, and its use is relatively uncommon (Koytzoumis, 2024).

Supporting patients and owners throughout the disease

The veterinary team plays a vital role in supporting both patients and their owners following a diagnosis. As a chronic, lifelong condition, management should take a holistic approach that focuses not only on treatment but also on maintaining the patient’s quality of life and supporting owners through the challenges of long-term care.

Managing owner expectations is imperative. Before treatment is initiated, the veterinary surgeon should ensure owners understand that Cushing’s disease is a lifelong condition requiring ongoing medication and regular veterinary monitoring. It is important to discuss whether owners feel confident administering medication consistently, can attend routine follow-up appointments and are able to manage the financial commitments associated with consultations, medication and laboratory testing. The team is vital in supporting owners throughout this process, providing reassurance, answering questions and ensuring they feel confident and informed during a pet’s lifelong management.

Furthermore, owners need to understand that the medications don’t cure the disease but can help manage it and improve clinical signs. As long as the veterinary surgeon is satisfied with the patient’s clinical status and monitoring results, the focus should be on effectively managing these clinical signs and ensuring the patient remains comfortable.

Veterinary nurses are well placed to provide practical advice that can help owners adapt to their dog’s changing needs.

Examples include:

• Never restrict access to drinking water, as dogs with Cushing’s disease will naturally drink more. Consider slow-drinking bowls to help reduce rapid water intake.
• Provide waterproof bedding, incontinence pads or increase opportunities for toileting if urinary accidents become problematic.
• Avoid walks through dense undergrowth or thorny vegetation, as the skin is often thin and fragile, making it more susceptible to injury.
• Adapt exercise to the dog’s ability, opting for shorter, gentler walks if muscle weakness or exercise intolerance develops.
• Provide appropriate mental stimulation, such as enrichment toys, scent work or food puzzles, when physical exercise needs to be reduced.
• Advise to keep a log of body weight, appetite, thirst, urination and overall demeanour, reporting any significant changes to the veterinary team promptly.

Veterinary nurses can provide written information, medication diaries and reliable educational resources to help improve owner confidence, encourage treatment compliance and strengthen the partnership between the owner and the veterinary team. By providing both clinical guidance and emotional support, veterinary nurses play a key role in helping owners successfully manage their dog’s condition while maintaining the best possible quality of life for their pet.

Conclusion

Cushing’s disease is a complex endocrine disorder that commonly affects older dogs and can significantly impact multiple body systems. Due to the gradual onset of clinical signs, recognition of subtle changes is essential to support early investigation and diagnosis.

Understanding the underlying causes, recognising common clinical signs and interpreting routine diagnostic findings enables veterinary professionals to identify patients requiring further investigation. While definitive diagnosis and treatment require veterinary involvement, veterinary nurses play a crucial role in supporting patients and owners through education, monitoring and long-term care.

With appropriate management and regular monitoring, many dogs with Cushing’s disease can maintain a good quality of life.

• This article appeared in VN Times (September/October 2026), Volume 26, Issue 9/10, Pages 8-10

Ellie Kohut has been in practice for seven years, but qualified as an RVN two years ago from Bottle Green Training. With a strong passion for exotic animals, she has recently finished the advanced programme in veterinary nursing small mammal certificate. In addition to her interest in exotics, Ellie enjoys consulting with pet owners and has a keen interest in emergency and critical care, as well as working with geriatric patients.