Pituitary Tumors and Hormonal Imbalances: How to Recognize and Respond

Brain & CognitionQ&AMeongsiljang Veterinary Advisory Board

Pituitary tumors disrupt hormone secretion, leading to conditions such as Cushing’s disease and diabetes insipidus. Early detection and precise imaging are crucial for successful treatment.

What Are Pituitary Tumors?

An anatomical illustration showing the location of a dog's brain and pituitary gland.

Pituitary tumors develop in the pituitary gland, the central hormone-regulating organ located in the middle of the brain. The most critical step is recognizing the signs of hormonal imbalance early on. If your pet exhibits excessive thirst, a distended abdomen, and hair loss for several weeks or more, these symptoms may indicate a pituitary issue rather than normal aging. Early diagnosis through advanced imaging, such as an MRI, is essential to maximize treatment options.

Why Do Hormonal Imbalances Occur?

The pituitary gland acts as the command center, sending signals to the adrenal glands, thyroid, and gonads to produce hormones. When a tumor develops in this area, it can cause these signals—such as ACTH (adrenocorticotropic hormone)—to either surge uncontrollably or cease entirely, leading to systemic hormonal imbalances. In dogs, the most common form is pituitary-dependent Cushing’s disease (PDH), where excessive ACTH secretion causes elevated cortisol levels. In cats, acromegaly, resulting from overproduction of growth hormone, is the most typical presentation.

Which Hormonal Imbalances Are Common by Species?

Item	Dog	Cat
Most common type	Pituitary-dependent Cushing's syndrome	Acromegaly (excess growth hormone)
Main hormone	ACTH → cortisol ↑	Excess growth hormone (GH) ↑
Representative symptoms	Polydipsia·polyuria, pendulous abdomen, alopecia	Poor diabetes control, enlargement of face·paws
Age of onset	Middle-aged to senior (individual variation)	Middle-aged to senior (individual variation)

General trends based on the veterinary internal medicine textbook, with individual variation.

Signs to Watch For

Hormonal imbalances develop gradually, so it’s crucial to catch them early when you first notice something seems “a bit off.”

Polyuria and polydipsia: A noticeable increase in water intake and urine output compared to usual.

Pot-bellied appearance: The abdomen becomes distended and sags, accompanied by muscle wasting.

Symmetrical hair loss: Hair falls out in a symmetrical pattern on both sides of the flanks or along the back.

Skin changes: The skin becomes thin, darkens, or develops acne-like rashes.

Neurological signs: Disorientation, head tilting, or seizures may indicate that a tumor has grown larger.

Illustration of an elderly dog showing suspected symptoms of a pituitary tumor

When to Seek Immediate Veterinary Care

If seizures, sudden blindness, circling behavior, or severe lethargy persist for more than 24 hours, it may indicate a pituitary macroadenoma—a large tumor pressing on surrounding brain tissue. In such cases, time is critical for prognosis. Please proceed immediately to an animal hospital equipped for emergency care.

How Is Diagnosis Made?

A definitive diagnosis requires both hormonal and imaging tests. If Cushing’s disease is suspected, we first perform a low-dose dexamethasone suppression test (LDDST) or an ACTH stimulation test. Once hormonal abnormalities are confirmed, we use MRI or CT scans to directly assess pituitary gland size. Tumors exceeding a certain size are classified as macroadenomas, which necessitates a different treatment strategy. The veterinarian determines whether a tumor is a macroadenoma by integrating imaging findings with neurological symptoms. However, imaging alone cannot determine whether a tumor is overproducing hormones, so endocrine function tests are always performed alongside imaging. Similarly, feline acromegaly is diagnosed by evaluating both growth hormone-related blood tests and MRI results.

Illustration of a veterinarian reading a pet brain MRI

How Is Treatment Managed?

Treatment depends on tumor size, the severity of hormonal symptoms, and the patient’s age.

Medical management: Medications such as trilostane, which suppress cortisol production, are used to control hormonal symptoms. This is often the first-line choice for small tumors or when the patient’s overall health is poor.

Radiation therapy: This is the most effective option for large tumors. It helps shrink the tumor, alleviate neurological symptoms, and extend survival time.

Surgery (transsphenoidal hypophysectomy): Available at select specialized veterinary hospitals, this procedure offers the potential for a cure but is technically challenging.

Your veterinarian will review the diagnostic results and develop a treatment plan tailored to your pet’s weight and age.

Key Precautions During Medication Therapy

Hormonal regulators like trilostane can lead to hypoadrenocorticism (Addisonian crisis) even with a slight overdose. If you notice vomiting, diarrhea, or severe lethargy, stop the medication immediately and contact your veterinarian. Regular hormone rechecks are not optional—they are essential. Your vet will determine the testing schedule based on your pet’s treatment progress and response to the medication, so please ensure you keep all scheduled appointments as directed.

How to Manage Care at Home

Daily care is just as important as treatment.

Water and Litter Boxes: Never restrict water intake during polyuria and polydipsia, and provide multiple litter boxes.

Diet: Consult your veterinarian to adjust the diet to a low-fat, high-protein formula to prevent weight gain.

Walks: If neurological symptoms are present, keep walks short and on non-slip surfaces.

Record-Keeping: Record weekly water intake, urination frequency, appetite, and weight to share at veterinary visits; this greatly assists in dosage adjustments.

For cats with acromegaly, diabetes control is central, so pay special attention to changes in insulin dosage.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Are pituitary tumors benign or malignant?

Most of these tumors are histologically benign (adenomas). However, because they are located in the center of the brain, they can become life-threatening if they grow large enough to compress surrounding nerves. Therefore, we assess the severity based on the tumor’s size and the associated symptoms.

Can pets live longer just by taking medication?

Cushing's disease caused by small tumors can often be managed long-term with medication. However, prognosis varies significantly from dog to dog depending on tumor size, the presence of neurological symptoms, and response to treatment, so it is important to work closely with your veterinarian to monitor progress. For large tumors, adding radiation therapy significantly extends survival time.

Is radiation therapy very painful?

The treatment itself is administered in several short sessions under general anesthesia. There is minimal pain, with temporary hair loss and mild skin irritation being the most common side effects.

Is it hereditary? Can it be prevented?

The exact genetic cause has not yet been identified. While complete prevention is difficult, adding hormone level tests to your pet’s health checkup if you notice excessive urination and hair loss in middle to older age can help with early detection.

How is feline acromegaly different from Cushing’s disease in dogs?

In dogs, Cushing’s disease is characterized by elevated cortisol levels, while in cats, acromegaly involves increased growth hormone. In feline patients, acromegaly is often first suspected when diabetes becomes difficult to control.

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References

[1] Withrow & MacEwen's Small Animal Clinical Oncology, 6th Edition, Ch. Tumors of the Endocrine System

[2] Veterinary Surgical Oncology, 2nd Ed, Ch. Intracranial Tumors

[3] The Cat, Clinical Medicine and Management, 2nd Edition, Ch. Neurologic Disorders

[4] Hu H, Barker A, Harcourt-Brown T, Jeffery N. Systematic review of brain tumor treatment in dogs. J Vet Intern Med, 2015