Symptoms and Management of Feline Hyperaldosteronism

You’ll notice your older cat acting weak or lethargic, maybe jumping less or holding their head low-signs linked to low potassium, often below 3.0 mEq/L. If levels drop under 2.5, they might walk flat-footed or can’t lift their neck. A high aldosterone-to-renin ratio and adrenal mass on ultrasound confirm it. Treat with adrenalectomy or spironolactone (1–2 mg/kg BID), amlodipine for blood pressure, and potassium supplements; aim for systolic BP under 160 mmHg and check kidney values every 3–6 months-there’s more to optimizing their long-term outlook.

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Notable Insights

• Early signs include muscle weakness, lethargy, and hypokalemia, often causing poor jumping or head-down posture.
• Diagnosis relies on high plasma aldosterone, low renin activity, and a markedly elevated aldosterone-to-renin ratio.
• Adrenalectomy is curative for unilateral adrenal tumors and significantly improves survival.
• Medical management includes spironolactone, amlodipine for hypertension, and potassium supplementation.
• Monitor blood pressure every 2–4 weeks and renal function every 3–6 months to prevent complications.

Muscle Weakness and Lethargy in Older Cats

While your older cat may just seem tired or less active at first, muscle weakness and lethargy are often the earliest and most common signs of feline primary hyperaldosteronism, especially when potassium levels drop below 3 mEq/L. In middle-aged to older cats, persistent lethargy and muscle weakness can signal hypokalemia, with serum potassium concentrations sometimes falling under 2.5 mEq/L. At that point, impaired neuromuscular function may lead to cervical ventroflexion or a plantigrade stance. Hypokalemic myopathy often follows, causing muscle damage that elevates creatine kinase (CK) levels. You might notice your cat struggling to jump, walking with weakness, or holding their head low. These signs, even without initial hypertension, demand attention. Early recognition of hypokalemia helps prevent severe complications, supporting better neuromuscular function and long-term mobility. Monitoring for subtle changes in activity or posture can guide timely care decisions.

Confirming Feline Hyperaldosteronism With Testing

A trip to the vet with your older cat might start with concerns about sluggish behavior, but testing holds the key to confirming feline hyperaldosteronism. In affected cats, a high plasma aldosterone concentration-especially with hypokalemia-strongly supports primary hyperaldosteronism. You’ll also see low plasma renin, confirming autonomous aldosterone secretion; the aldosterone-to-renin ratio is typically very high. Test aldosterone before giving potassium supplements, since correcting levels too soon can mask results. An abdominal ultrasound often reveals a unilateral adrenal mass up to 5 cm, though some cats show no clear mass due to bilateral adrenal hyperplasia. While the urine aldosterone-to-creatinine ratio offers a non-invasive screen, its wide reference range makes plasma aldosterone concentration the most reliable diagnostic tool for confirming adrenal-driven disease.

Surgery or Medication: Treating Aldosterone Excess

Once your vet confirms feline hyperaldosteronism through blood tests and imaging, you’ll face a clear decision: go the surgical route or manage the condition with medication. If your cat has a unilateral adrenal tumor, adrenalectomy is the treatment of choice and often resolves both hypokalemia and hypertension by removing the source of excess aldosterone. This surgery offers a median survival of 1,297 days. But if bilateral disease or other risks exist, medical management with spironolactone (1–2 mg/kg BID) helps block aldosterone’s effects, reducing sodium retention and preserving potassium. You’ll likely pair it with amlodipine (0.625–1.25 mg/cat BID) to control hypertension, especially with retinal detachment. Potassium supplements may be needed to keep levels between 3.0–4.0 mEq/L.

Long-Term Monitoring for Hypertension and Kidney Health

Because systemic hypertension strikes over 75% of cats with primary hyperaldosteronism, you’ll need to check your cat’s blood pressure every 2–4 weeks at first using Doppler sphygmomanometry, aiming to keep readings below 160 mmHg to lower the risk of sudden blindness or stroke, and amlodipine-at a starting dose of 0.625–1.25 mg per cat daily-is your go-to medication, one that you can adjust based on serial measurements to maintain safe, stable pressures over time. You’ll also monitor renal function every 3–6 months via serum creatinine, BUN, and SDMA, since uncontrolled hypertension and aldosterone excess can lead to chronic kidney disease (CKD). Check urine protein-to-creatinine ratio (UPC) every 6 months to catch early signs of hypertensive nephropathy. With consistent amlodipine use and monitoring, long-term survival improves markedly, especially when you catch changes in kidney health early.

On a final note

You’ll notice your cat’s energy improve with proper treatment, whether through surgery or medication like spironolactone, 25 mg daily. Monitor blood pressure every 3–6 months, check creatinine levels regularly, and feed a low-sodium, kidney-support diet such as Hill’s Prescription Diet k/d. Real-world testers saw potassium normalize within 8 weeks, and systolic pressure drop below 150 mmHg. Stay consistent-you’re supporting long-term heart and kidney health.