CONDITION
Hyperaldosteronism in Cats
Hyperaldosteronism in cats describes a pattern in which the adrenal glands produce too much of a hormone called aldosterone. Aldosterone helps regulate the balance of sodium and potassium in the blood, and when present in excess, it tends to drive potassium levels down and blood pressure up. The condition arises most often from a small tumour in one or both adrenal glands, though in some cats the cause remains unclear. Owners may notice increased thirst and urination, occasional weakness or a stiff, stilted gait, or sometimes no outward signs at all—the pattern may only come to light during blood tests taken for other reasons. Muscle weakness, when present, often reflects the low potassium levels that result from aldosterone's effects on the kidneys. Some cats show high blood pressure on routine screening, which may prompt further investigation. This page explores the signals that may suggest hyperaldosteronism, what is happening inside the body to produce those signals, how the condition is investigated through blood tests and imaging, and the approaches that exist for managing it over time. The goal is to help you understand the shape of the condition and the conversations that may follow.
Why this matters now
Hyperaldosteronism in cats tends to appear in middle-aged to older animals, typically between eight and fifteen years of age, though younger cats can occasionally be affected. No strong breed predisposition has been identified, and the condition arises equally in males and females. In many cases, the underlying adrenal abnormality develops quietly over months or years before signs become apparent.
The condition often progresses slowly, with potassium levels falling gradually as aldosterone production rises. Some cats show subtle signs early on—mild muscle weakness or increased thirst—that may come and go or worsen incrementally. In other cats, the pattern remains silent until blood pressure rises to a level that prompts concern, or until routine blood work reveals markedly low potassium. The rate of progression varies considerably between individuals, and the trajectory can be influenced by whether one or both adrenal glands are involved.
Signals & patterns
Early signals
Increased thirst and urination
Many cats begin drinking more water than usual and producing larger volumes of urine. This happens because low potassium levels can interfere with the kidneys' ability to concentrate urine, prompting the body to compensate by taking in more fluid.
Intermittent muscle weakness
Some owners notice their cat seems slightly less steady on their feet, or occasionally sits in an unusual posture with the hind legs splayed. The weakness may be subtle at first and can come and go, reflecting fluctuations in potassium levels that affect normal muscle contraction.
Weight loss despite normal appetite
A cat may continue to eat well but lose body condition slowly over weeks or months. The metabolic effects of chronic potassium depletion and the energy cost of compensating for electrolyte imbalance can contribute to gradual weight loss.
Occasional neck ventroflexion
In some cats, the head and neck begin to droop forward, particularly when the animal is walking or standing. This posture reflects weakness in the muscles that normally hold the head upright, and tends to appear when potassium levels are markedly low.
Later signals
Persistent stilted gait
As potassium depletion continues, the hind limbs may appear stiff and the cat may walk with a shuffling or plantigrade stance, placing the hocks on the ground rather than walking on the toes. This reflects more severe muscle weakness and can make jumping or climbing difficult.
Vision changes or eye abnormalities
High blood pressure sustained over time can damage the small blood vessels in the retina, occasionally leading to sudden blindness or visible changes in the appearance of the eye. Owners may notice dilated pupils, blood within the eye, or a cat that seems disoriented or reluctant to move in dim light.
Reduced activity and reluctance to move
Cats with advanced muscle weakness may spend more time resting and show less interest in play, grooming, or exploration. The effort required to move with weakened muscles can make previously routine activities uncomfortable or exhausting.
Click to read about the biological mechanisms
How this is usually investigated
Options & trade-offs
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