Feline Addison’s disease review urges earlier suspicion in cats

A new review on feline hypoadrenocorticism is a reminder that Addison’s disease in cats is less a zebra than a diagnostic blind spot. Writing in Schweizer Archiv für Tierheilkunde, F.S. Boretti and N.S. Sieber-Ruckstuhl describe a disorder that is rare, but clinically important because it often presents with vague, waxing-and-waning signs that can mimic more common gastrointestinal, renal, or critical care problems. Their message is straightforward: clinicians should think about hypoadrenocorticism sooner, especially in cats with chronic GI signs, poor growth, or episodes of hypovolemic shock. (pure.ed.ac.uk)

That framing fits with the broader literature. A 2024 review covering 40 years of published feline cases found that reported patients ranged from 7 months to 14 years old, with cats younger than 6 years overrepresented. Most reported cats were domestic shorthairs or longhairs, but British Shorthairs were the next most common breed in the compiled literature, supporting the source article’s note that this breed may deserve extra scrutiny when compatible signs are present. (pure.ed.ac.uk)

The challenge is that the clinical picture is often nonspecific. Across published cases, common signs included anorexia, lethargy, vomiting, weight loss, dehydration, and weakness, and acute presentations could include collapse, severe dehydration, and shock. Laboratory changes often reflected mineralocorticoid deficiency, including hyponatremia, hyperkalemia, hypochloremia, azotemia, and hyperphosphatemia, but not every cat followed the expected pattern. In the 40-year review, 10 of 48 reported cats had a normal sodium:potassium ratio, underscoring why reliance on electrolyte screening alone can miss cases. (pure.ed.ac.uk)

On diagnosis, the review aligns with current reference guidance: the ACTH stimulation test remains the confirmatory test of choice in cats. The recent feline review notes that published protocols have varied, but all include a resting cortisol measurement and at least one post-ACTH sample, while current recommendations cited there use baseline, 60-minute, and 90-minute samples. Supporting laboratory guidance from AAHA-associated interpretive materials says a resting cortisol above 2.0 µg/dL is considered inconsistent with feline hypoadrenocorticism, while baseline cortisol below 1 µg/dL with post-ACTH cortisol below 2 µg/dL supports the diagnosis. Michigan State University’s veterinary diagnostic laboratory similarly emphasizes low baseline cortisol with lack of response to ACTH stimulation, and notes that endogenous ACTH can help support a diagnosis of primary disease. (pure.ed.ac.uk)

One reason diagnosis can be messy in practice is prior drug exposure. The 2024 review notes that corticosteroids and progestogens can suppress adrenal function in cats, and that oral prednisolone at 2 mg/kg daily or higher for at least 14 days has been associated with low or low-normal resting cortisol and inadequate ACTH responses, with normalization reported within 30 days after stopping treatment. That matters for referral and first-opinion teams alike, because a cat that partially improves after fluids or steroids may still have underlying hypoadrenocorticism rather than a resolved GI flare. (pure.ed.ac.uk)

Treatment remains familiar in concept, but less settled in feline-specific evidence. Long-term management generally uses glucocorticoid and mineralocorticoid replacement, including prednisolone plus either fludrocortisone or desoxycorticosterone pivalate. Still, the evidence base is largely case reports and small series, and the 2024 review points out that the available DOCP product, Zycortal, is licensed for dogs and has not had its safety assessed in cats. That leaves clinicians extrapolating from canine medicine while tailoring dose intervals and monitoring to individual feline patients. (pure.ed.ac.uk)

Why it matters: For veterinary professionals, this is less about a brand-new disease insight than a diagnostic mindset shift. Cats with chronic intermittent vomiting, poor growth, unexplained dehydration, weak pulses, azotemia, or shock may not look endocrine at first glance, and some won’t have the classic electrolyte signature. The practical takeaway is to move ACTH stimulation testing higher on the workup list when the history is waxing and waning, especially in younger cats and British Shorthairs, and to interpret cortisol results carefully if the patient has recently received steroids. Earlier recognition can prevent repeat symptomatic treatment cycles, reduce the risk of missing an Addisonian crisis, and help practices set realistic long-term expectations for pet parents. (pure.ed.ac.uk)

What to watch: The next step for this niche field is better standardization, including more consistent ACTH stimulation protocols, stronger data on breed predisposition, and larger outcome studies to clarify how cats do on DOCP versus fludrocortisone over time. A newer multi-case publication on 41 cats suggests that the evidence base is finally expanding, so clinicians should expect feline Addison’s guidance to become more specific in the next few years. (pubmed.ncbi.nlm.nih.gov)