CONDITION
Adrenal Tumours
The adrenal glands sit near the kidneys and produce hormones that regulate metabolism, blood pressure, and the body's response to stress. A tumour in one of these glands can alter the normal pattern of hormone production, leading to a range of changes that unfold gradually over weeks or months. In dogs, the most common scenario involves excess cortisol, which can produce a distinctive picture: increased thirst and urination, a pot-bellied appearance, thinning skin, and changes in coat quality. In cats, adrenal tumours are less common and may be discovered incidentally or in the context of hormone imbalances. Many owners arrive at this page having noticed a slow accumulation of signs — perhaps a dog drinking more than usual, or a coat that no longer grows back after clipping. Others may have had a mass detected during imaging for an unrelated concern. The tumour itself may be benign or malignant, and it may or may not be actively secreting hormones; that distinction shapes both the picture the owner sees and the approach to investigation. This page explores what adrenal tumours can look like in practice, the mechanisms that connect gland changes to observable signs, how these tumours are identified and characterised, and the range of approaches — from monitoring to surgery to medical management — that exist depending on the tumour's behaviour, location, and the animal's overall picture.
Why this matters now
Adrenal tumours tend to appear in middle-aged to older dogs and cats, most often between eight and eleven years of age, though they can develop at any point in adult life. Certain breeds, including Poodles, Dachshunds, and Terriers, appear in clinical records more frequently, though the reasons for this are not fully understood. In many cases, the tumour has been present and growing quietly for months or years before any outward change becomes noticeable.
The timeline of change varies widely depending on whether the tumour is producing hormones and how quickly it is growing. Some tumours remain small and silent for years, discovered only when imaging is performed for another reason. Others trigger a gradual accumulation of signs over weeks to months as hormone levels rise, or as the growing mass begins to press on nearby blood vessels or organs. Malignant tumours may eventually spread to the liver, lungs, or lymph nodes, though this progression can be slow and unpredictable.
Signals & patterns
Early signals
Increased thirst and urination
An owner may notice the water bowl being emptied more often, or the dog asking to go outside more frequently, particularly overnight. This pattern can develop gradually and may be mistaken for age-related change or a urinary infection.
Changes in appetite or weight
Some animals become noticeably hungrier, eating with more urgency or scavenging in ways they did not before. Others may lose weight despite eating normally, or gain weight in unusual patterns, particularly around the abdomen.
Coat thinning or slow regrowth
The fur may become sparse, dull, or slow to grow back after clipping. The skin underneath can feel thin or papery to the touch. These changes often appear symmetrically on both sides of the body.
Muscle weakness or fatigue
The animal may tire more easily on walks, struggle to jump onto furniture, or show less interest in play. Muscle loss can be subtle at first, most noticeable over the hind legs and along the spine.
Pot-bellied appearance
The abdomen may begin to sag or distend, giving a rounded profile even in animals that are not overweight. This develops over weeks to months and can be accompanied by thinning of the limbs.
Later signals
Panting or restlessness
The animal may pant heavily without exertion, particularly at night, and seem unable to settle. This can reflect changes in metabolism, muscle function, or the body's ability to regulate temperature and stress.
Skin bruising or fragility
The skin may bruise easily from minor contact, or develop thin areas that tear or bleed with little provocation. Wounds may heal more slowly than expected.
Collapse or weakness episodes
Some animals experience sudden episodes of weakness or collapse, particularly if the tumour has affected blood pressure, electrolyte balance, or blood flow to major organs. These episodes may resolve on their own but tend to recur.
Abdominal swelling or discomfort
As the tumour grows larger, it may cause visible swelling in the flank or a reluctance to lie in certain positions. In some cases, the mass can be felt through the body wall or detected as a firmness during gentle handling.
Click to read about the biological mechanisms
How this is usually investigated
Investigation often begins with a careful history and physical examination, followed by blood tests that measure hormone levels and assess how the body is responding to any hormonal excess. Imaging of the abdomen helps to locate the tumour, estimate its size, and look for signs of local invasion or distant spread. The combination of hormone measurements and imaging usually clarifies whether a tumour is present, which gland is involved, and whether it appears to be producing hormones.
Blood biochemistry and haematology
Basal cortisol and ACTH stimulation test
Low-dose dexamethasone suppression test
Abdominal ultrasound
CT or MRI
Options & trade-offs
Management is shaped by the type of tumour, whether it is producing hormones, how large it has grown, and the overall health and age of the animal. Some owners and vets choose a combination of approaches, adjusting over time as the picture evolves. No single path suits all cases, and each option carries its own practical and medical considerations.
Surgical removal (adrenalectomy)
This involves removing the affected adrenal gland, usually through an open abdominal incision or, in some centres, by keyhole surgery. The goal is to remove the tumour entirely, particularly if it is confined to the gland and has not invaded major blood vessels. Recovery typically takes several weeks, and hormone levels may need monitoring and support during that time.
Trade-offs: Surgery carries significant risk, particularly if the tumour has grown into the vena cava or if the animal has other health concerns. Older animals, those with widespread metastases, or those with poor anaesthetic tolerance may find the procedure less feasible. Even when successful, surgery does not prevent recurrence if malignant cells remain.
Medical management with trilostane or mitotane
These drugs reduce the production or release of cortisol from the adrenal tissue, helping to control the signs of hormonal excess without removing the tumour. Doses are adjusted over weeks or months based on clinical response and repeat blood tests. Many animals live comfortably for months or years on this approach.
Trade-offs: Medical management does not address the tumour itself, and a growing mass may eventually cause problems unrelated to hormone levels. Monitoring is ongoing, and some animals experience side effects including lethargy, vomiting, or electrolyte imbalances. Malignant tumours may continue to grow or spread despite hormone control.
Active monitoring
For non-functional tumours discovered incidentally, or for animals with mild or stable signs, observation with repeat imaging and clinical assessment every few months is sometimes chosen. This allows the tumour's behaviour to be tracked without immediate intervention, and decisions can be revisited if the situation changes.
Trade-offs: Monitoring does not alter the course of the disease, and a tumour may grow or begin producing hormones over time. Some owners find the uncertainty difficult, and delays may narrow options if intervention becomes needed later.
Palliative and supportive care
In cases where surgery is not feasible and medical management is poorly tolerated or ineffective, care focuses on managing individual signs such as muscle weakness, skin infections, high blood pressure, or changes in appetite and energy. This may include adjustments to diet, medication for secondary problems, and close attention to quality of life.
Trade-offs: This approach does not slow tumour growth or control hormone excess directly, and progressive decline may occur over weeks to months. It tends to suit animals with advanced disease, significant comorbidities, or owners seeking a gentler path.
Common misconceptions
"If the tumour is benign, it does not need any treatment."
Benign adrenal tumours can still produce large amounts of hormone, leading to serious and progressive metabolic changes even though the tumour itself will not spread. The decision to treat is usually based on what the tumour is doing, not just its cellular classification.
"Surgery always cures adrenal tumours."
Surgery can be curative if the tumour is completely removed and has not spread, but some tumours invade local structures or have already seeded distant sites by the time they are detected. Recurrence or progression can occur even after apparently successful removal, particularly with malignant types.
"Once hormone levels are controlled with medication, the problem is resolved."
Medication can effectively manage the signs caused by excess hormones, but it does not shrink the tumour or prevent it from growing. A tumour that continues to enlarge may eventually cause problems through local invasion or metastasis, regardless of hormone control.
Related conditions
Adrenocortical Carcinoma
Adrenocortical carcinoma is a malignant tumour arising from the outer layer of the adrenal gland, and represents one of the specific forms an adrenal tumour can take. These cancers often produce excess cortisol and tend to behave more aggressively than benign adrenal adenomas, with a greater likelihood of spread to other organs.
Pheochromocytoma in Dogs
Pheochromocytoma arises from the inner portion of the adrenal gland rather than the outer cortex, but can appear very similar on imaging and may present with overlapping signs. Distinguishing between cortical tumours and pheochromocytoma often requires specialised tests or examination of tissue, as both can cause an adrenal mass and both may be found incidentally or produce hormonal effects.
Hyperaldosteronism in Cats
Hyperaldosteronism in cats is most often caused by an adrenal tumour that produces aldosterone rather than cortisol or other hormones. The tumour itself arises from the same outer layer of the adrenal gland, but the pattern of signs differs—reflecting which hormone is being overproduced—with affected cats typically showing muscle weakness and high blood pressure rather than the features associated with cortisol excess.
Steroid Hepatopathy
Steroid hepatopathy describes changes in the liver that develop in response to prolonged exposure to excess cortisol, and can occur when an adrenal tumour produces too much of this hormone. The liver accumulates glycogen and undergoes structural changes that alter enzyme levels and contribute to the pot-bellied appearance sometimes seen in affected dogs.
Pituitary Macroadenoma
A pituitary macroadenoma can produce similar signs to a cortisol-secreting adrenal tumour, as both cause excess cortisol in the bloodstream—one by directly secreting cortisol from the adrenal gland, the other by releasing hormones that drive both adrenal glands to overproduce it. Distinguishing between these two causes is an important part of investigating a pattern consistent with Cushing's syndrome.
Understanding how adrenal tumours are investigated and managed can help frame conversations about what is practical and meaningful in an individual case. The broader picture of ageing, metabolic health, and quality of life often shapes these decisions as much as the tumour itself. Other pages in the Longevity & Healthspan section explore related endocrine patterns and the ways that hormonal changes interact with ageing and resilience.