Cushing’s disease — medically known as hyperadrenocorticism — is one of the most common hormonal disorders in middle-aged and older dogs. It occurs when the body produces too much cortisol, the primary stress hormone, leading to a wide range of systemic changes. Although Cushing’s is a serious and lifelong condition, it is manageable with the right treatment, and many dogs go on to live comfortable, happy lives after diagnosis.
What Is Cushing’s Disease in Dogs?
Cushing’s disease results from chronically elevated cortisol levels. Cortisol is produced by the adrenal glands — two small glands that sit near the kidneys — in response to adrenocorticotropic hormone (ACTH) released by the pituitary gland in the brain. When this regulatory system malfunctions, the adrenal glands produce cortisol continuously, regardless of actual physiological need.
Cortisol plays essential roles in regulating metabolism, the immune system, and the stress response. When levels are chronically too high, virtually every body system is affected: muscles weaken, the skin thins, the immune system is suppressed, and metabolic function deteriorates.
Cushing’s disease is most commonly seen in dogs over six years of age and has a higher prevalence in certain breeds, including Poodles, Dachshunds, Boxers, Boston Terriers, and Yorkshire Terriers. Female dogs are slightly more commonly affected than males.
Types: Pituitary-Dependent vs Adrenal-Dependent
Approximately 80 to 85 percent of Cushing’s cases in dogs are pituitary-dependent hyperadrenocorticism (PDH). This occurs when a tumor — usually benign and microscopic — in the pituitary gland produces excess ACTH, which in turn overstimulates both adrenal glands to produce excess cortisol.
The remaining 15 to 20 percent of cases involve an adrenal tumor — either benign (adenoma) or malignant (carcinoma) — that produces cortisol autonomously, independent of pituitary signaling. Adrenal tumors typically affect only one gland, while PDH causes both glands to enlarge.
A third, iatrogenic form of Cushing’s occurs when dogs receive prolonged high-dose corticosteroid therapy (such as prednisone) for another condition. In this case, treating the cause means carefully and gradually tapering the steroid under veterinary guidance, rather than using Cushing’s-specific medication.
Signs and Symptoms of Cushing’s Disease
The classic symptoms of Cushing’s disease develop gradually over months to years, which is why many owners initially attribute them to normal aging. The most recognizable signs include increased thirst and urination, increased appetite, a pot-bellied appearance caused by muscle wasting and fat redistribution, and lethargy.
Skin changes are prominent in dogs with Cushing’s. The skin becomes thin, fragile, and prone to easy bruising. Hair may thin or fall out symmetrically on the trunk while the head and legs remain unaffected. Skin infections (pyoderma) and calcinosis cutis — calcium deposits under the skin — are also common complications.
Additional signs include panting, muscle weakness, a reluctance to exercise, and recurrent urinary tract infections due to immune suppression. Neurological signs such as disorientation or changes in behavior may appear if a pituitary tumor is large (a ‘macro-tumor’).
How Vets Diagnose Cushing’s Disease
Diagnosing Cushing’s disease requires a combination of clinical assessment, bloodwork, urinalysis, and specific hormonal tests. Routine bloodwork often reveals elevated liver enzymes, high cholesterol, and low urine specific gravity. These are suggestive but not diagnostic.
The two most common confirmatory tests are the low-dose dexamethasone suppression test (LDDST) and the ACTH stimulation test. The LDDST measures whether a small dose of dexamethasone suppresses cortisol production, which it should in normal dogs but fails to do in dogs with Cushing’s. The ACTH stimulation test measures how aggressively the adrenal glands respond to hormonal stimulation.
Once Cushing’s is confirmed, abdominal ultrasound is typically used to assess adrenal gland size and look for adrenal tumors. If PDH is suspected and the pituitary tumor may be large, MRI or CT of the brain may be recommended.
Treatment Options and Management
The most widely used medication for pituitary-dependent Cushing’s is trilostane (Vetoryl), which blocks the enzyme responsible for cortisol synthesis. Trilostane is given daily and requires regular monitoring because over-suppression of cortisol can cause a potentially fatal condition called an Addisonian crisis.
Mitotane (Lysodren) is an older alternative that destroys cortisol-producing cells in the adrenal cortex. It is also effective but requires careful induction and monitoring protocols. Some veterinary oncologists prefer it for certain cases.
Adrenal tumors may be treated surgically if the tumor is benign and accessible, though surgery carries significant risk. Inoperable or malignant adrenal tumors may be managed medically. Regular monitoring — including ACTH stimulation testing every few months — is essential regardless of treatment approach to ensure cortisol levels remain in a safe range.
Frequently Asked Questions
Is Cushing’s disease fatal in dogs?
Cushing’s disease itself is not immediately fatal, but unmanaged it significantly reduces quality of life and shortens lifespan. With proper diagnosis and treatment, many dogs live comfortably for years after diagnosis. The biggest risks are complications such as diabetes, high blood pressure, blood clots, and secondary infections.
How long can a dog live with Cushing’s disease?
Survival time varies depending on the type, severity, and response to treatment. Dogs with pituitary-dependent Cushing’s treated with trilostane or mitotane often live two to three or more years after diagnosis. Dogs with malignant adrenal tumors generally have a shorter prognosis, particularly if the tumor has spread.
Can Cushing’s disease in dogs be cured?
There is no cure for pituitary-dependent Cushing’s — it requires lifelong medical management. Adrenal tumors can sometimes be cured surgically if removed completely and before metastasis, but surgery carries significant risk. Iatrogenic Cushing’s from steroid therapy resolves when the medication is tapered under veterinary supervision.
What triggers Cushing’s disease in dogs?
In most cases, Cushing’s is caused by a spontaneous pituitary tumor that overproduces ACTH. The exact trigger for tumor formation is not fully understood. Genetic factors, chronic inflammation, or hormonal dysregulation over time may play roles. Long-term corticosteroid therapy is a preventable cause that owners can discuss with their vet.
Is Cushing’s disease painful for dogs?
Cushing’s disease is not typically painful in the traditional sense, but it causes significant discomfort and reduced quality of life. Muscle weakness, lethargy, excessive thirst and hunger, and skin complications can make affected dogs uncomfortable. Treatment aimed at normalizing cortisol levels generally leads to noticeable improvement in energy and wellbeing within weeks.