Hyperaldosteronism in Cats

What Is Hyperaldosteronism in Cats?

Hyperaldosteronism, also called Conn syndrome or aldosteronism, happens when one or both adrenal glands produce too much aldosterone. Aldosterone is the hormone that tells the kidneys to hold sodium and dump potassium. Too much of it leads to low blood potassium (hypokalemia), muscle weakness, and high blood pressure. In cats the usual cause is a benign adrenal tumor (adenoma) or, less often, an adenocarcinoma or enlargement of both adrenal glands.

This is different from everyday chronic kidney disease, which can also raise blood pressure and change potassium levels. In hyperaldosteronism the primary problem is the adrenal hormone, and kidney changes may follow. It is also the opposite pattern from Addison’s disease (too little adrenal hormones), which is well described in dogs and rare in cats. Cushing’s disease is excess cortisol, not aldosterone.

Signs Owners Notice

• Sudden or episodic weakness, especially in the hind legs
• A dropped neck posture (chin tucked toward the chest) from low potassium
• Increased thirst and urination; compare other causes under drinking a lot of water
• Vision loss or dilated pupils from hypertensive eye damage
• Reduced appetite, vomiting, or weight loss
• Sometimes a palpable mass in the abdomen found by a vet

Diagnosis

Bloodwork typically shows low potassium and sometimes high sodium. Blood pressure is often markedly elevated. Your vet may measure plasma aldosterone (often high) and renin (often low), and use ultrasound or CT to look at the adrenal glands. Kidney values may be normal or elevated if high blood pressure has already damaged the kidneys.

The workup also rules out other causes of weakness and hypokalemia, including chronic kidney disease, diabetes, and certain drugs. Chest imaging may be added if an adrenal cancer that could spread is suspected.

Treatment and Outlook

• Surgery: removing the affected adrenal gland (adrenalectomy) can be curative when a single benign tumor is present and the cat is a good anesthetic candidate.
• Medical management: potassium supplementation, blood-pressure medicines, and an aldosterone-blocking drug such as spironolactone when surgery is not possible or both glands are involved.
• Eye and kidney support: treating hypertensive damage and any concurrent CKD.

Cats that have a benign tumor successfully removed often do very well. Cats managed only with medicine can stay comfortable for months to years with close monitoring of potassium, blood pressure, and kidney values. Malignant adrenal tumors carry a more guarded outlook.

Practical Tips for US Pet Owners

• Ask for blood pressure checks at senior wellness visits — hypertension is easy to miss at home.
• Do not ignore sudden hind-end weakness or a neck that will not lift; low potassium is an emergency for some cats.
• If your cat is on blood-pressure medicine that is not working, ask whether aldosterone testing makes sense.
• Find a nearby practice through veterinary clinic listings.

Key Takeaways

• Feline hyperaldosteronism is excess aldosterone, usually from an adrenal tumor.
• Hallmarks are low potassium, muscle weakness, and high blood pressure.
• Surgery can cure single-gland disease; medicine helps when surgery is not an option.

FAQ

Is Conn syndrome common in cats?
It is underdiagnosed rather than truly rare. Specialty clinics see it more often in older cats with hypertension and hypokalemia.

Can diet alone fix low potassium from hyperaldosteronism?
No. The hormone drive continues until the adrenal source is removed or blocked; potassium supplements help but do not cure the cause.

Does this disease affect dogs the same way?
Primary hyperaldosteronism is reported far more often in cats than in dogs.