Primary Hyperaldosteronism in Cats

Primary hyperaldosteronism in cats is an endocrine disease caused by autonomous overproduction of aldosterone, a hormone made by the adrenal glands. Aldosterone helps regulate sodium, potassium, and blood pressure. When too much is produced, cats tend to lose potassium in the urine and retain sodium and water. That combination can lead to hypokalemia, systemic hypertension, muscle weakness, and damage to organs such as the eyes, kidneys, heart, and brain. Most reported cases are in middle-aged to older cats.

In many cats, the underlying cause is an aldosterone-secreting adrenal tumor. These tumors may be benign or malignant. Some cats do not have a discrete tumor and instead have bilateral adrenal hyperplasia, meaning the hormone-producing tissue is enlarged and overactive. Because the signs can overlap with chronic kidney disease, hyperthyroidism, diabetes, or general aging, this condition is likely underrecognized.

What makes this disease important is that some cats first come in for signs that seem unrelated, such as sudden blindness from high blood pressure, a dropped neck from severe low potassium, or increased thirst and urination. Others are found during a workup for persistent hypertension or unexplained hypokalemia. Early recognition matters because treatment can improve comfort, reduce complications, and in some cases offer long-term control or even surgical resolution.

For pet parents, the key takeaway is that primary hyperaldosteronism is treatable, but the best plan depends on the cat’s overall health, imaging findings, blood pressure, kidney values, and whether one adrenal gland or both are involved. Your vet may recommend conservative, standard, or advanced care paths based on your cat’s needs and your goals for treatment.

Diagnosis usually starts with a careful physical exam and baseline testing. Your vet will often recommend bloodwork to look for low potassium, changes in sodium, kidney values, and other clues, along with a urinalysis and blood pressure measurement. Persistent systemic hypertension in a cat without an obvious explanation should raise suspicion, especially when it occurs with hypokalemia or muscle weakness.

The next step is confirming inappropriate aldosterone excess. This is typically done with serum aldosterone testing, ideally interpreted alongside plasma renin activity when available. In primary hyperaldosteronism, aldosterone is high despite the body not needing it, and renin is often low or suppressed. Not every clinic can run all endocrine testing in-house, so samples may need to be sent to a reference laboratory.

Imaging is a major part of the workup. Abdominal ultrasound can identify an adrenal mass, assess the opposite adrenal gland, and look for spread to nearby structures. CT may be recommended before surgery because it gives more detail about tumor size, local invasion, and whether major blood vessels are involved. That information helps determine whether surgery is realistic and how much risk is involved.

Your vet may also screen for common look-alikes or concurrent disease, including chronic kidney disease, hyperthyroidism, diabetes mellitus, and other causes of hypertension or hypokalemia. In real-world practice, diagnosis is often a combination of compatible signs, documented hypertension or hypokalemia, hormone testing, and imaging findings rather than one single test result.

Most feline cases are caused by an adrenal cortical tumor that secretes aldosterone independently of the normal renin-angiotensin-aldosterone system. These tumors may be adenomas or carcinomas. A smaller group of cats has bilateral adrenal hyperplasia, where both adrenal glands are overactive without a single obvious tumor. Either way, the result is the same: excess aldosterone drives potassium loss and raises blood pressure.

Primary hyperaldosteronism is most often recognized in middle-aged to older cats. Current references do not describe a strong breed or sex predisposition. Because many affected cats are seniors, they may also have chronic kidney disease, hyperthyroidism, or diabetes, which can blur the clinical picture and delay diagnosis.

Risk factors are less about lifestyle and more about being in the age group where adrenal disease becomes more likely. A history of unexplained weakness, recurrent low potassium, or hypertension without heart or thyroid disease should prompt a closer look. Cats with sudden retinal changes or blindness from hypertension may also need evaluation for endocrine causes, including hyperaldosteronism.

It is important to distinguish primary hyperaldosteronism from secondary hyperaldosteronism. In the secondary form, another disease process activates the hormone system appropriately, such as dehydration or heart disease. In primary hyperaldosteronism, the adrenal tissue is acting autonomously, so treatment focuses on the adrenal disorder itself and the complications it causes.

There is no known way to prevent primary hyperaldosteronism in cats because the condition is usually linked to spontaneous adrenal tumors or adrenal hyperplasia rather than diet, environment, or routine care choices. That said, earlier detection can reduce the risk of severe complications such as retinal detachment, blindness, or profound muscle weakness.

Regular wellness visits become especially important in middle-aged and senior cats. Blood pressure measurement, routine chemistry panels, and urinalysis can uncover hypertension, low potassium, or kidney changes before a cat looks obviously ill. If your cat already has chronic kidney disease, hyperthyroidism, diabetes, or unexplained weakness, asking your vet whether blood pressure and electrolytes should be checked is reasonable.

At home, watch for subtle changes. A cat that stops jumping, seems weaker in the back legs, drinks more, or holds the neck in a drooped position should be evaluated promptly. Sudden vision changes are an emergency. While these signs do not prove hyperaldosteronism, they are important clues that something more than normal aging may be happening.

The most realistic prevention strategy is complication prevention through monitoring. Once diagnosed, consistent follow-up helps your vet adjust medication, protect the eyes and kidneys from uncontrolled hypertension, and catch changes that might shift the treatment plan from medical management to referral or surgery.

Prognosis depends on the underlying cause, whether one or both adrenal glands are involved, how severe the hypertension and hypokalemia are, and whether there is concurrent kidney disease or other illness. Many cats improve noticeably once potassium and blood pressure are controlled. Strength, appetite, and activity often get better over days to weeks, although recovery can be slower if muscle weakness has been severe.

Cats managed medically can still have a meaningful quality of life, especially when blood pressure and potassium respond well to treatment. They usually need lifelong monitoring and medication adjustments. Prognosis is more guarded when hypertension has already caused eye, kidney, heart, or neurologic damage, or when the adrenal tumor is invasive or metastatic.

For selected cats with a unilateral adrenal tumor, adrenalectomy can offer the most definitive control. Recovery after surgery requires close monitoring because blood pressure, electrolytes, and hormone balance can shift quickly in the postoperative period. Some cats do very well long term after successful surgery, but the procedure is not appropriate or safe for every patient.

Your vet can give the most useful outlook after reviewing imaging, lab results, and your cat’s response to initial treatment. In Spectrum of Care terms, prognosis is not about choosing one “best” path. It is about matching the treatment intensity to your cat’s disease, comfort, and your goals while keeping complications under control.