Laboratory Clues Hinting at Cushing’s Syndrome in Pets 🐾

By Dr Duncan Houston, BVSc

Before Cushing’s syndrome is definitively diagnosed, there are often early indicators that raise suspicion. These clues come from standard lab tests such as the complete blood count (CBC), serum chemistry, and urinalysis—tests commonly performed during routine or diagnostic visits. Recognizing these subtle markers allows veterinarians to determine when specific Cushing’s testing is warranted. In this 2025 veterinary update, Dr Duncan Houston breaks down these diagnostic signals clearly for pet parents. 🩺

🔍 What Is Cushing’s Syndrome?

Cushing’s syndrome, or hyperadrenocorticism, is caused by prolonged elevation of cortisol levels. This may result from a pituitary tumor (the most common cause), adrenal tumors, or chronic steroid use. Signs develop gradually, including excessive drinking and urination, hair loss, thinning skin, and a pot-bellied appearance in dogs. Detecting subtle lab changes helps catch the disease early. 🧬

🧪 Initial Screening Tests: Where Suspicion Starts

While these clues don't confirm Cushing's, they strengthen the case for specific tests like the Low-Dose Dexamethasone Suppression Test or ACTH Stimulation Test.

📉 The Stress Leukogram

A stress leukogram is a pattern of white blood cell changes influenced by cortisol. If your dog appears calm, but the bloodwork reflects stress patterns, internal cortisol excess may be to blame.

• ↑ Neutrophils: Primary defenders in the bloodstream.
• ↓ Lymphocytes: Often suppressed by corticosteroids.
• ↓ Eosinophils: Another group dampened by excess cortisol.

This pattern is detected via a CBC. While non-specific, it’s an important red flag—especially in patients without obvious stress or infection. 🧫

⚠️ Elevated Alkaline Phosphatase (ALP)

ALP is a liver enzyme that skyrockets in many dogs with Cushing’s due to the enzyme’s steroid-induced isoform. Although not harmful itself, persistently high ALP can suggest excessive cortisol or steroid use.

This increase is far more dramatic than what’s typically seen in liver disease. ALP values may reach several times the normal range without other liver enzymes being elevated. 🧬

💉 Elevated Cholesterol

High cholesterol levels are common in endocrine disorders, including Cushing’s. Abnormal fat metabolism, influenced by cortisol, leads to elevated serum cholesterol. Though not directly harmful in dogs as it is in humans, it flags endocrine imbalance. 🥼

💧 Dilute Urine and Hidden Infections

Excessive drinking due to cortisol leads to dilute urine. Specific gravity is often <1.015 in affected dogs. A weak immune system also increases the risk of urinary tract infections (UTIs), but the dilute urine may mask the presence of white blood cells or bacteria.

Up to 20% of dogs with Cushing’s have silent (inapparent) UTIs. A urine culture is the best way to detect this. If your pet has dilute urine and no obvious symptoms, culturing the sample is wise. 🧪🐶

🐱 Feline Cushing’s: Different Lab Patterns

Cats are less likely to show the same laboratory hints as dogs. In fact, many cats with Cushing’s disease do not show:

• A stress leukogram
• Elevated ALP
• Elevated cholesterol

Most feline Cushing’s patients are diabetic. If the diabetes becomes unusually difficult to control despite proper insulin use, Cushing’s may be the underlying cause.

🚨 Clue: Hard-to-Regulate Diabetes

Cats with Cushing’s often require very high insulin doses (>2 units/kg) and still have poor glucose control. If you suspect insulin resistance, test for endocrine disorders including Cushing’s. 🧫

🧭 Putting the Puzzle Together

No single lab clue confirms Cushing’s. But when multiple red flags align with clinical signs (e.g., panting, thinning coat, pot belly), your vet may recommend follow-up testing:

• Low-Dose Dexamethasone Suppression Test: best confirmatory test.
• ACTH Stimulation Test: useful for therapy monitoring or iatrogenic Cushing’s.
• Urine Cortisol:Creatinine Ratio: helpful screening test.

🧼 Sample Collection Tips

• 💉 Blood should be drawn before 10 AM for optimal cortisol rhythm accuracy.
• 💧 Urine samples should be collected at home (first morning urine is ideal) to minimize stress-induced cortisol elevation.
• 🧫 Store samples appropriately and transport promptly.

📱 Ask A Vet Support

Unsure if lab values warrant further testing? Get real-time help through the Ask A Vet app. Upload your pet’s lab work, chat with licensed vets, and receive personalized guidance. From interpreting a stress leukogram to deciding if a cortisol curve is needed, our team is here for you. 🐾📊

💡 Final Thoughts

Spotting Cushing’s early means looking deeper at subtle clues. A combination of high ALP, low eosinophils, dilute urine, or recurrent UTIs could be more than just coincidence. Talk to your vet and use trusted tools like Ask A Vet to plan next steps confidently.

Early action leads to better control, less discomfort, and a happier life for your pet. ❤️