Serious severity

Addison's Disease (Hypoadrenocorticism)

A rare hormonal disorder in which the adrenal glands fail to make enough of their essential hormones. Very uncommon in cats but potentially life-threatening, as it disrupts the body's salt, water and stress balance.

⚠️ Common symptoms

Lethargy and weaknessPoor or absent appetiteWeight lossVomiting and sometimes diarrhoeaIncreased thirst and urinationDehydrationWaxing-and-waning illness that seems to improve then relapseCollapse or crisis in severe cases

Addison's disease, known to vets as hypoadrenocorticism, is the mirror image of the better-known Cushing's disease: instead of making too much hormone, the adrenal glands make too little. These small glands, tucked just in front of the kidneys, produce hormones that quietly run some of the body's most important background systems — the balance of salt and potassium, the regulation of water, and the ability to cope with physical stress. When they fail, the effects ripple through the whole body.

The condition is genuinely rare in cats, far less common than in dogs, and that rarity is part of the problem. Its early signs — tiredness, a picky appetite, a little weight loss, the odd bout of vomiting — are so ordinary and so easily blamed on something else that the disease is often not suspected until a cat becomes seriously unwell. A hallmark is illness that comes and goes: a cat seems to rally, then slips back again, never quite thriving.

The most dangerous moment is an 'Addisonian crisis', when hormone levels drop too low to maintain blood pressure and electrolyte balance. A cat may suddenly collapse, become profoundly weak, and go into shock. This is a true emergency, and without prompt treatment with fluids and hormone support it can be fatal. Because a crisis can be the first obvious sign, some cats are only diagnosed once they are already critically ill.

The good news is that, once identified, Addison's is very treatable. Diagnosis relies on blood tests — often revealing tell-tale changes in sodium and potassium — confirmed by a specific stimulation test of the adrenal glands. Treatment replaces the missing hormones for life, with regular monitoring to keep the doses right and extra cover during times of stress or illness. With committed care, a cat with Addison's disease can live a full and comfortable life.

🔍 Causes

Addison's disease results from the adrenal glands, which sit near the kidneys, no longer producing enough of two vital groups of hormones — glucocorticoids (such as cortisol) and mineralocorticoids (such as aldosterone). Most often this is because the body's own immune system gradually destroys the adrenal tissue, but it can also follow damage from infection, tumours or bleeding. A second form, iatrogenic Addison's, can occur when long-term steroid medication is stopped too abruptly, leaving the suppressed glands unable to respond. The disease is genuinely rare in cats, which is one reason it is often missed at first.

🛡 Prevention

There is no reliable way to prevent the common immune-mediated form of Addison's disease, but the iatrogenic form can be avoided by never stopping long-term steroid treatment suddenly — always taper it under veterinary guidance. Because the early signs are so vague and come and go, the most useful thing an owner can do is seek veterinary advice for a cat that is repeatedly 'off colour', losing weight or having episodes of vomiting, so that testing can be done before a crisis develops.

💊 Treatment

Addison's disease is managed rather than cured, and with the right treatment cats can do well. An acute 'Addisonian crisis' is a medical emergency treated with intravenous fluids, correction of dangerous electrolyte imbalances and steroid support. Long-term management centres on replacing the missing hormones: a mineralocorticoid (given by injection or tablet) to control salt and potassium balance, usually alongside a low dose of a glucocorticoid such as prednisolone, with extra given at times of stress or illness. Cats need regular blood tests to fine-tune the doses, and treatment is lifelong.

When to see a vet: See your vet promptly for any cat with persistent lethargy, poor appetite, weight loss or repeated vomiting, especially where the illness seems to wax and wane. Treat sudden collapse, severe weakness or a cat that is cold and unresponsive as an emergency needing immediate care — an Addisonian crisis can be fatal within hours without treatment. Mention if your cat has recently been on and then stopped steroid medication, as this is an important clue.

⚕️ Medical disclaimer

  • This information is educational only and is not a substitute for veterinary advice.
  • Symptoms overlap between conditions — only a vet can diagnose accurately.
  • Never withhold treatment or self-medicate based on information found online.
  • When in doubt, call your vet. Early intervention almost always leads to better outcomes.

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