Q: Is there an at-home cortisol test for my dog or cat?

While salivary cortisol testing is used in human medicine and emerging biosensor technologies are being developed, at-home cortisol testing is not currently a standard or recommended diagnostic tool in veterinary medicine. Cortisol testing requires prescription medications, precise timing, and laboratory analysis, and should only be performed by a veterinarian.

# Cortisol Testing for Cushings and Addisons: ACTH Stimulation vs LDDST Tests ## Key Takeaways - The ACTH stimulation test is the definitive diagnostic method for Addison's disease (hypoadrenocorticism) by assessing the adrenal glands' response to synthetic ACTH, and it is also used to monitor treatment efficacy for Cushing's disease. - The Low-Dose Dexamethasone Suppression Test (LDDST) is the preferred screening test for Cushing's syndrome (hyperadrenocorticism) in dogs due to its higher sensitivity (90-95%) and its ability to help differentiate between pituitary-dependent and adrenal-dependent forms of the disease. - Stress can significantly impact cortisol levels, potentially leading to false positives in baseline cortisol measurements; the ACTH stimulation test is less susceptible to stress-induced elevations than baseline cortisol alone. - Medications containing glucocorticoids (e.g., prednisone, dexamethasone) will interfere with cortisol testing by suppressing the hypothalamic-pituitary-adrenal (HPA) axis, necessitating disclosure to the veterinarian. - At-home cortisol testing is not currently a standard diagnostic tool in veterinary medicine; accurate diagnosis requires prescription medications, precise timing, and laboratory analysis performed by a veterinarian. --- When a [dog](/knowledge/veterinary-medicine/clinical-methods/dog) or [cat](/knowledge/veterinary-medicine/clinical-methods/cat) shows signs of Cushing's syndrome (hyperadrenocorticism) or Addison's disease (hypoadrenocorticism), the path to a correct diagnosis depends on measuring cortisol, the primary stress hormone produced by the adrenal glands. The two most common dynamic tests used in veterinary practice are the ACTH stimulation test and the [low-dose dexamethasone suppression test](/knowledge/diagnostics/endocrinology/endocrine-testing-low-dose-dexamethasone-suppression-for-cushings-disease) (LDDST). The ACTH stimulation test is the definitive method for diagnosing Addison's disease and is also used to monitor Cushing's treatment. The LDDST is the preferred screening test for Cushing's syndrome in dogs because it has higher sensitivity for pituitary-dependent disease. This article explains how these tests work, when each is used, and what the results mean for your pet. **Owner Triage Summary:** If your pet is drinking excessively, urinating more, has a pot-bellied appearance, hair loss, or lethargy, contact your veterinarian. Do not attempt to diagnose or treat these conditions at home. Cortisol testing requires prescription medications, precise timing, and laboratory analysis. If your pet is collapsed, vomiting, or severely weak, seek emergency veterinary care immediately, as these can be signs of an Addisonian crisis. ## At a Glance: ACTH Stimulation vs LDDST | Feature | ACTH Stimulation Test | Low-Dose Dexamethasone Suppression Test (LDDST) | |-----|-----------|-------------------------| | **Primary Use** | Diagnose Addison's disease; monitor Cushing's treatment | Screen for and differentiate Cushing's syndrome in dogs | | **What It Measures** | Adrenal gland response to synthetic ACTH | Cortisol response to dexamethasone suppression | | **Time Required** | 1 to 2 hours | 8 hours | | **Blood Samples** | 2 (baseline and post-ACTH) | 3 (baseline, 4-hour, 8-hour) | | **Best For** | Confirming adrenal insufficiency; monitoring trilostane or mitotane therapy | Diagnosing Cushing's syndrome, especially pituitary-dependent | | **Sensitivity for Cushing's** | Moderate (approximately 60-85% in dogs) | High (approximately 90-95% in dogs) | | **Can It Diagnose Addison's?** | Yes, this is the gold standard | No, not appropriate | | **Stress Effects** | Less affected by stress than baseline cortisol | Can be affected by stress, but less than baseline alone | ## Understanding Cortisol and the Adrenal Glands Cortisol is a glucocorticoid hormone produced by the zona fasciculata of the adrenal cortex. It is essential for maintaining health, regulating metabolism, modulating the immune system, and responding to stress [1]. Cortisol is lipophilic and travels in the blood bound to cortisol-binding globulin (CBG) and albumin, with only a small fraction (approximately 10%) unbound and biologically active [1]. The production of cortisol follows a cascade: the hypothalamus releases corticotropin-releasing hormone (CRH), which stimulates the pituitary gland to release adrenocorticotropic hormone (ACTH), which then stimulates the adrenal cortex to produce cortisol [2]. This is known as the hypothalamic-pituitary-adrenal (HPA) axis. In companion animals, particularly dogs and cats, cortisol plays a significant role in the development and progression of endocrine diseases [3]. When this delicate balance is disrupted, two main disorders can occur: 1. **Cushing's syndrome (hyperadrenocorticism):** The adrenal glands produce too much cortisol. This can be due to a pituitary tumor producing excess ACTH (pituitary-dependent) or an adrenal tumor producing cortisol independently (adrenal-dependent). 2. **Addison's disease (hypoadrenocorticism):** The adrenal glands produce insufficient cortisol. This is typically immune-mediated destruction of the adrenal cortex, leading to deficiencies in both glucocorticoids and mineralocorticoids. Distinguishing between these two conditions is critical because their treatments are opposite, and giving the wrong medication can be life-threatening. ## The ACTH Stimulation Test The ACTH stimulation test is a dynamic endocrine test that directly assesses the functional reserve of the adrenal cortex. It involves measuring cortisol levels before and after the administration of synthetic ACTH. ### How the ACTH Stimulation Test Works The test is based on the principle that a healthy adrenal gland will respond to exogenous ACTH by increasing cortisol production. In a dog or cat with normal adrenal function, cortisol levels will rise significantly after ACTH administration. In a patient with Addison's disease, the adrenal glands are damaged or atrophied and cannot respond, so cortisol levels remain low. In a patient with Cushing's syndrome, the adrenal glands are hyperplastic or contain a tumor, so they may produce an exaggerated response. ### Procedure 1. **Baseline blood sample:** A blood sample is taken to measure resting cortisol. 2. **ACTH administration:** Synthetic ACTH (cosyntropin) is injected intravenously or intramuscularly. 3. **Post-ACTH blood sample:** A second blood sample is taken 30 to 60 minutes after ACTH administration (for cosyntropin) or 60 to 120 minutes (for compounded ACTH gel). 4. **Cortisol measurement:** Both samples are analyzed for serum cortisol concentration. ### Interpreting ACTH Stimulation Results | Diagnosis | Baseline Cortisol | Post-ACTH Cortisol | |------|----------|-----------| | **Normal** | Normal | Significant rise (typically > 8-10 µg/dL in dogs) | | **Addison's Disease** | Low or low-normal | Minimal to no rise (typically < 2 µg/dL in dogs) | | **Cushing's Syndrome** | Normal to high | Exaggerated rise (typically > 20-22 µg/dL in dogs) | | **Iatrogenic Cushing's (from steroid medication)** | Low | Minimal response | ### Advantages of the ACTH Stimulation Test - **Gold standard for Addison's disease:** This test is the definitive method for diagnosing hypoadrenocorticism [2]. A blunted or absent cortisol response to ACTH confirms the diagnosis. - **Monitoring tool:** The ACTH stimulation test is used to monitor dogs receiving trilostane or mitotane therapy for Cushing's disease. Cortisol levels are measured to ensure the medication dose is appropriate and not causing adrenal suppression. - **Faster than LDDST:** The test can be completed in 1 to 2 hours, making it more convenient for owners and less stressful for the patient. ### Limitations of the ACTH Stimulation Test - **Lower sensitivity for Cushing's:** The ACTH stimulation test has a lower sensitivity for diagnosing Cushing's syndrome compared to the LDDST. Some dogs with mild Cushing's disease may have a normal response to ACTH stimulation. - **Can miss adrenal-dependent Cushing's:** Dogs with adrenal tumors may not always show an exaggerated response. - **Cost:** The test can be more expensive than a baseline cortisol measurement, though comparable to LDDST. ## The Low-Dose Dexamethasone Suppression Test (LDDST) The LDDST is a longer test that evaluates the negative feedback mechanism of the HPA axis. It is based on the principle that dexamethasone, a synthetic glucocorticoid, should suppress cortisol production in a healthy animal by inhibiting ACTH release from the pituitary gland. ### How the LDDST Works In a normal animal, administration of a low dose of dexamethasone will suppress pituitary ACTH secretion, leading to a decrease in cortisol production. In a dog with Cushing's syndrome, this suppression does not occur properly. The pattern of cortisol suppression (or lack thereof) can also help differentiate between pituitary-dependent and adrenal-dependent Cushing's syndrome. ### Procedure 1. **Baseline blood sample:** A blood sample is taken to measure resting cortisol. 2. **Dexamethasone administration:** A low dose of dexamethasone (0.01 mg/kg IV in dogs) is injected. 3. **4-hour blood sample:** A second blood sample is taken 4 hours after dexamethasone administration. 4. **8-hour blood sample:** A third blood sample is taken 8 hours after dexamethasone administration. 5. **Cortisol measurement:** All three samples are analyzed for serum cortisol concentration. ### Interpreting LDDST Results | Pattern | Baseline Cortisol | 4-Hour Cortisol | 8-Hour Cortisol | Interpretation | |-----|----------|---------|---------|--------| | **Normal** | Normal | Suppressed (< 1.5 µg/dL) | Suppressed (< 1.5 µg/dL) | No Cushing's | | **Pituitary-Dependent Cushing's** | Normal to high | Variable | Suppressed (< 50% of baseline) or > 1.5 µg/dL | Cushing's confirmed; may show partial suppression | | **Adrenal-Dependent Cushing's** | Normal to high | Not suppressed | Not suppressed (< 50% of baseline) | Cushing's confirmed; no suppression suggests adrenal tumor | ### The "Suppression" Pattern A key feature of the LDDST is the interpretation of the 4-hour and 8-hour cortisol values: - **If cortisol is suppressed at 4 hours and 8 hours** (below 1.5 µg/dL or less than 50% of baseline), this indicates a normal response, ruling out Cushing's syndrome. - **If cortisol is not suppressed at 4 hours but is suppressed at 8 hours** (to less than 50% of baseline), this is highly suggestive of pituitary-dependent Cushing's disease. - **If cortisol is not suppressed at either 4 or 8 hours**, this could indicate either pituitary-dependent or adrenal-dependent Cushing's syndrome. Further testing (such as abdominal ultrasound or measurement of endogenous ACTH) may be needed to differentiate. ### Advantages of the LDDST - **Higher sensitivity for Cushing's:** The LDDST has a higher sensitivity (approximately 90-95%) for diagnosing Cushing's syndrome in dogs compared to the ACTH stimulation test. - **Differentiates pituitary vs. adrenal:** The pattern of suppression can help determine whether the disease is pituitary-dependent or adrenal-dependent, which guides treatment and prognosis. - **Screening tool:** The LDDST is often used as a first-line screening test when Cushing's syndrome is suspected. ### Limitations of the LDDST - **Time-consuming:** The test requires 8 hours, meaning the dog must stay at the veterinary clinic for most of the day. - **Not useful for Addison's:** The LDDST cannot diagnose Addison's disease. In fact, a dog with Addison's disease would show very low cortisol at all time points, but this is not a safe or appropriate way to diagnose the condition. - **Stress effects:** Stress can affect cortisol levels and potentially influence test results [4]. - **Three blood samples:** Requires three separate blood draws, which can be stressful for the patient. ## Comparing the Two Tests: Which One to Choose? The choice between the ACTH stimulation test and the LDDST depends on the clinical suspicion and what information the veterinarian needs. ### When to Use the ACTH Stimulation Test - **Suspected Addison's disease:** If a dog presents with weakness, collapse, vomiting, diarrhea, or an inability to mount a stress response, Addison's disease is a primary differential. The ACTH stimulation test is the gold standard for confirming this diagnosis [2]. - **Monitoring Cushing's treatment:** Dogs on trilostane or mitotane require regular ACTH stimulation tests to monitor adrenal function and adjust medication doses. - **Evaluating iatrogenic Cushing's:** If a dog has been on long-term steroids and develops signs of Cushing's, the ACTH stimulation test can help determine if the adrenal glands have been suppressed. ### When to Use the LDDST - **Suspected Cushing's syndrome:** If a dog has classic signs of Cushing's (polyuria, polydipsia, polyphagia, pot-bellied appearance, hair loss, panting), the LDDST is the preferred screening test due to its higher sensitivity. - **Differentiating pituitary vs. adrenal disease:** The LDDST can help distinguish between pituitary-dependent and adrenal-dependent Cushing's, which is important for treatment planning. - **Atypical cases:** If the ACTH stimulation test results are equivocal, the LDDST may provide additional information. ### A Practical Approach In many veterinary practices, the diagnostic approach is as follows: 1. **Baseline cortisol:** A single baseline cortisol measurement can be a useful screening tool. A very low baseline cortisol (< 2 µg/dL) is highly suggestive of Addison's disease, while a high baseline cortisol (> 5 µg/dL) may support Cushing's, but it is not diagnostic. 2. **ACTH stimulation test:** If Addison's disease is suspected, proceed directly to the ACTH stimulation test. 3. **LDDST:** If Cushing's syndrome is suspected, the LDDST is the preferred test. 4. **Additional testing:** If the LDDST confirms Cushing's but cannot differentiate pituitary from adrenal disease, an abdominal ultrasound or endogenous ACTH measurement may be recommended. ## Factors That Can Affect Cortisol Testing Several factors can influence cortisol test results and should be considered when interpreting them. ### Stress Stress is a potent stimulator of cortisol secretion. A stressed or anxious dog may have elevated baseline cortisol levels, which could confound test results [4]. The effect of stress on the ACTH stimulation test is less pronounced because the test measures the adrenal response to exogenous ACTH, which is less affected by endogenous ACTH fluctuations. ### Sedation Many dogs require sedation for blood collection or other procedures. The choice of sedative can significantly impact cortisol levels. A 2024 study evaluated the effects of butorphanol, dexmedetomidine, and trazodone on serum cortisol concentrations in healthy dogs [4]. The study found that butorphanol significantly increased both basal and post-ACTH cortisol concentrations compared to saline. Dexmedetomidine and trazodone did not significantly affect cortisol levels [4]. This is a critical finding for veterinary practitioners, as butorphanol is a commonly used sedative. ### Medications Any medication that contains glucocorticoids (such as prednisone, prednisolone, or dexamethasone) will interfere with cortisol testing. Oral, topical, or injectable steroids can suppress the HPA axis and lead to false results. It is essential to inform your veterinarian about all medications your pet is receiving. ### Time of Day Cortisol secretion follows a circadian rhythm in many species. However, in dogs and cats, this rhythm is less pronounced than in humans, and random cortisol measurements are generally acceptable. Late-night salivary cortisol measurements are a standard screening test for Cushing's syndrome in humans [5, 6], but this is not a common test in veterinary medicine. ### Assay Variability Cortisol assays can vary between laboratories and between different assay methods [1]. Automated immunoassays lack specificity and show significant inter-assay differences [1]. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) offers improved specificity and sensitivity, but the cortisol cut-offs used in dynamic tests have not been fully validated for these assays [1]. This is why it is important to use the same laboratory for serial monitoring. ## The Role of Salivary Cortisol Testing Salivary cortisol testing has become a valuable tool in human medicine for screening Cushing's syndrome [5, 6]. Salivary cortisol reflects the free, biologically active fraction of cortisol in the blood and is not affected by changes in cortisol-binding globulin [6]. It is simple, non-invasive, and can be collected at home, making it an attractive option. In veterinary medicine, salivary cortisol testing is not yet a standard diagnostic tool, but it is an area of active research. The non-invasive nature of saliva collection could be particularly useful for stress-free testing in dogs and cats [5]. However, more research is needed to establish reference ranges and validate the test for veterinary use. ## Emerging Technologies in Cortisol Detection Advances in biosensor technology are paving the way for more accessible and rapid cortisol testing. Molecularly imprinted polymers (MIPs) have been developed for sensitive and selective cortisol detection [7]. These electrochemical sensors have demonstrated a limit of detection of 5.8 pM, which is more than three orders of magnitude lower than typical cortisol concentrations in human fluids [7]. While these technologies are primarily being developed for human diagnostics, they may eventually have applications in veterinary medicine, including point-of-care testing. Another area of development is the use of native mass spectrometry to quantify glucocorticoid binding to anti-cortisol antibodies [8]. This research is improving our understanding of antibody specificity and cross-reactivity, which is essential for developing more accurate immunoassays [8]. ## Case Studies and Clinical Scenarios ### Scenario 1: A Dog with Polyuria and Polydipsia A 9-year-old Labrador Retriever presents with increased thirst, urination, and appetite, along with a pot-bellied appearance and hair loss. The veterinarian suspects Cushing's syndrome. **Recommended approach:** The LDDST is the preferred test. Baseline cortisol is 4.5 µg/dL. After dexamethasone administration, the 4-hour cortisol is 3.8 µg/dL, and the 8-hour cortisol is 1.2 µg/dL. This pattern (suppression at 8 hours to less than 50% of baseline) is consistent with pituitary-dependent Cushing's disease. ### Scenario 2: A Dog with Collapse and Weakness A 5-year-old mixed-breed dog presents with acute weakness, vomiting, and collapse. The dog is bradycardic and dehydrated. The veterinarian suspects Addisonian crisis. **Recommended approach:** An ACTH stimulation test is performed. Baseline cortisol is 0.8 µg/dL. Post-ACTH cortisol is 1.0 µg/dL. This blunted response confirms the diagnosis of Addison's disease. Immediate treatment with intravenous fluids, glucocorticoids, and mineralocorticoids is initiated. ### Scenario 3: Monitoring a Dog on Trilostane A 10-year-old dog with confirmed pituitary-dependent Cushing's disease has been on trilostane for 3 months. The owner reports improvement in clinical signs but wants to ensure the dose is correct. **Recommended approach:** An ACTH stimulation test is performed 4 to 6 hours after trilostane administration. The post-ACTH cortisol should be between 2 and 5 µg/dL for optimal control. If the cortisol is too high, the dose may need to be increased. If it is too low, the dose should be decreased to avoid iatrogenic Addison's disease. ## Limitations and When to Contact a Veterinarian This article provides general information about cortisol testing in dogs and cats. It is not a substitute for professional veterinary advice, diagnosis, or treatment. Breed-level information cannot predict individual responses to testing or disease progression. Every animal is unique, and only a veterinarian can interpret test results in the context of a complete physical examination, medical history, and other diagnostic findings. **Contact your veterinarian immediately if your pet shows any of the following:** - **Emergency red flags:** Collapse, severe weakness, vomiting, diarrhea, or inability to stand. These can be signs of an Addisonian crisis, which is a life-threatening emergency. - **Signs of Cushing's syndrome:** Increased thirst and urination, increased appetite, pot-bellied appearance, hair loss, thinning skin, or recurrent skin infections. - **Signs of Addison's disease:** Lethargy, decreased appetite, weight loss, vomiting, diarrhea, shaking, or weakness. - **Concerns about medications:** If your pet is on corticosteroids or medications for Cushing's disease, do not stop or change the dose without consulting your veterinarian. ## Frequently Asked Questions ### 1. What is the difference between the ACTH stimulation test and the LDDST? The ACTH stimulation test measures the adrenal gland's ability to produce cortisol in response to synthetic ACTH, and it is the gold standard for diagnosing Addison's disease. The LDDST evaluates the negative feedback mechanism of the HPA axis by measuring cortisol suppression after dexamethasone administration, and it is the preferred screening test for Cushing's syndrome due to its higher sensitivity. ### 2. Which test is better for diagnosing Cushing's disease in dogs? The LDDST is generally considered better for diagnosing Cushing's syndrome because it has a higher sensitivity (approximately 90-95%) compared to the ACTH stimulation test (approximately 60-85%). The LDDST can also help differentiate between pituitary-dependent and adrenal-dependent disease. ### 3. Can the ACTH stimulation test diagnose Addison's disease? Yes, the ACTH stimulation test is the definitive diagnostic test for Addison's disease. A blunted or absent cortisol response to ACTH administration confirms the diagnosis. ### 4. How long does each test take? The ACTH stimulation test takes 1 to 2 hours. The LDDST takes 8 hours because it requires blood samples at baseline, 4 hours, and 8 hours after dexamethasone administration. ### 5. Can stress affect my pet's cortisol test results? Yes, stress can elevate baseline cortisol levels and potentially affect test results [4]. The ACTH stimulation test is less affected by stress than baseline cortisol measurements because it measures the adrenal response to exogenous ACTH. ### 6. What medications can interfere with cortisol testing? Any medication containing glucocorticoids (such as prednisone, prednisolone, or dexamethasone) can interfere with cortisol testing by suppressing the HPA axis. Certain sedatives, such as butorphanol, can also increase cortisol levels [4]. Always inform your veterinarian about all medications your pet is receiving. ### 7. Is there an at-home cortisol test for my dog or cat? While salivary cortisol testing is used in human medicine [5, 6] and emerging biosensor technologies are being developed [7], at-home cortisol testing is not currently a standard or recommended diagnostic tool in veterinary medicine. Cortisol testing requires prescription medications, precise timing, and laboratory analysis, and should only be performed by a veterinarian. ### 8. How often does my dog need an ACTH stimulation test while on Cushing's medication? Dogs on trilostane or mitotane typically require ACTH stimulation tests every 2 to 4 weeks initially to adjust the dose, then every 3 to 6 months for long-term monitoring. Your veterinarian will recommend a specific monitoring schedule based on your dog's response to treatment. --- ## Related Clinical & Scientific Guides * [Thyroid Testing in Cats: Diagnosing Hyperthyroidism and T4 Fluctuations](/knowledge/veterinary-medicine/at-home-diagnostics/thyroid-testing-in-cats-diagnosing-hyperthyroidism-and-t4-fluctuations) * [Joint Fluid Analysis in Dogs: Diagnosing Septic Arthritis vs Immune-Mediated](/knowledge/veterinary-medicine/at-home-diagnostics/joint-fluid-analysis-in-dogs-diagnosing-septic-arthritis-vs-immune-mediated) * [Blood Glucose Curves for Diabetic Pets: In-Clinic vs At-Home Monitoring](/knowledge/veterinary-medicine/at-home-diagnostics/blood-glucose-curves-for-diabetic-pets-in-clinic-vs-at-home-monitoring)