Canine Cushing Disease Diagnosis Treatment
By DVM Rounds·April 1, 2026·1 question
🩺Internal Medicine
🧭 Routing
This is a classic case of canine hyperadrenocorticism (Cushing's disease) with diagnostic test results provided. The questions pertain to differentiation (pituitary vs. adrenal), trilostane dosing, monitoring protocols, and long-term management, all of which fall squarely within the expertise of an internal medicine specialist.
🩺Elena VasquezInternal Medicine Specialist
Excellent, thank you for the clear summary. My endocrinology sub-agent has provided a detailed protocol, which aligns perfectly with my approach. Here is my synthesis and plan for your patient.
Based on the signalment, classic clinical signs, and definitive ACTH stimulation and LDDS results, you have a solid diagnosis of hyperadrenocorticism. The lack of suppression on the LDDS is typical, but as you know, it doesn't reliably differentiate the cause. Our next step is to distinguish between pituitary-dependent (PDH) and an adrenal tumor (ADH), as this dictates our entire therapeutic strategy.
My endocrinology colleague detailed the two primary methods for differentiation:
Abdominal Ultrasound: This is my preferred next step. It's non-invasive and provides a wealth of additional information. With PDH, we expect to see two normal-to-plump, symmetrical adrenal glands. An adrenal tumor will typically present as a unilateral mass with contralateral adrenal atrophy.
Endogenous ACTH (eACTH): This is also a valid option. A normal-to-high eACTH level points to PDH, while a low or undetectable level indicates an adrenal tumor is suppressing the pituitary.
Given that approximately 85% of cases are PDH, we can formulate a treatment plan with that high probability in mind. If ultrasound reveals an adrenal tumor, we must pivot to a surgical consultation.
Assuming this is PDH, the treatment of choice is trilostane. I fully concur with the endocrinology specialist's recommendation to start with twice-daily (BID) dosing for more stable, all-day cortisol control.
* Starting Dose: 1-2 mg/kg PO BID, given with food to maximize absorption. For a Miniature Poodle, this will likely require a compounding pharmacy to create an appropriately sized capsule.
* Monitoring Protocol: This is critical.
* 10-14 Day Recheck: Perform an ACTH stimulation test 4-6 hours after the morning dose of trilostane. This timing is crucial. We are also assessing electrolytes and clinical signs.
* 1 Month & 3 Month Rechecks: Repeat the post-pill ACTH stim and clinical assessment.
* Long-Term: Once stable, recheck every 3-6 months.
* Therapeutic Goal: The target for the post-stimulation cortisol is between 1.5-5.4 µg/dL (40-150 nmol/L). However, resolution of clinical signs (PU/PD, polyphagia) is the ultimate goal. We treat the patient, not the number.
Advise the owner that this is lifelong therapy requiring consistent monitoring. They should watch for signs of over-suppression (lethargy, vomiting, inappetence, diarrhea), which could indicate iatrogenic Addison's disease.
This is a very manageable disease. Let's start with the abdominal ultrasound to confirm PDH, and then we can confidently initiate this trilostane protocol.
Confidence: High. This is a classic presentation with a well-established management path.
Based on the signalment, classic clinical signs, and definitive ACTH stimulation and LDDS results, you have a solid diagnosis of hyperadrenocorticism. The lack of suppression on the LDDS is typical, but as you know, it doesn't reliably differentiate the cause. Our next step is to distinguish between pituitary-dependent (PDH) and an adrenal tumor (ADH), as this dictates our entire therapeutic strategy.
My endocrinology colleague detailed the two primary methods for differentiation:
Given that approximately 85% of cases are PDH, we can formulate a treatment plan with that high probability in mind. If ultrasound reveals an adrenal tumor, we must pivot to a surgical consultation.
Assuming this is PDH, the treatment of choice is trilostane. I fully concur with the endocrinology specialist's recommendation to start with twice-daily (BID) dosing for more stable, all-day cortisol control.
* Starting Dose: 1-2 mg/kg PO BID, given with food to maximize absorption. For a Miniature Poodle, this will likely require a compounding pharmacy to create an appropriately sized capsule.
* Monitoring Protocol: This is critical.
* 10-14 Day Recheck: Perform an ACTH stimulation test 4-6 hours after the morning dose of trilostane. This timing is crucial. We are also assessing electrolytes and clinical signs.
* 1 Month & 3 Month Rechecks: Repeat the post-pill ACTH stim and clinical assessment.
* Long-Term: Once stable, recheck every 3-6 months.
* Therapeutic Goal: The target for the post-stimulation cortisol is between 1.5-5.4 µg/dL (40-150 nmol/L). However, resolution of clinical signs (PU/PD, polyphagia) is the ultimate goal. We treat the patient, not the number.
Advise the owner that this is lifelong therapy requiring consistent monitoring. They should watch for signs of over-suppression (lethargy, vomiting, inappetence, diarrhea), which could indicate iatrogenic Addison's disease.
This is a very manageable disease. Let's start with the abdominal ultrasound to confirm PDH, and then we can confidently initiate this trilostane protocol.
Confidence: High. This is a classic presentation with a well-established management path.
Endocrine Specialist
Here is a detailed plan for the 9-year-old Miniature Poodle with confirmed hyperadrenocorticism:
The primary methods for differentiation are:
* Abdominal Ultrasound:
* PDH: Typically presents with bilaterally symmetric adrenal glands that are normal to mildly enlarged. Rarely, one adrenal gland may appear slightly atrophied due to the influence of a pituitary tumor.
* ADH: Characterized by a unilateral adrenal mass (often >2 cm in diameter) with contralateral adrenal atrophy. This is due to the autonomous cortisol production from the tumor suppressing endogenous ACTH, leading to atrophy of the other adrenal gland.
* Endogenous ACTH (eACTH) Concentration:
* PDH: eACTH levels are typically normal to high, as the pituitary gland is overproducing ACTH.
* ADH: eACTH levels are low to undetectable, as the autonomous cortisol production from the adrenal tumor suppresses pituitary ACTH release via negative feedback.
* Starting Dose: For a Miniature Poodle, a common starting dose is 0.5-1 mg/kg orally BID (twice daily).
* Rationale for BID: Many specialists advocate for BID dosing from the outset. Studies suggest that BID administration provides more consistent cortisol suppression throughout the day, potentially leading to better clinical control and fewer "breakthrough" signs compared to SID dosing, especially in smaller breeds.
* Administration: Always administer trilostane with food, as this significantly improves absorption.
* Example: For a 5 kg Miniature Poodle:
* Starting at 0.5 mg/kg BID: 2.5 mg BID (using the smallest available capsule size, typically 10 mg, you might need to use a compounding pharmacy or consider 10 mg SID initially if BID is not feasible with available capsule sizes, then adjust).
* Starting at 1 mg/kg BID: 5 mg BID (again, compounding may be necessary depending on capsule sizes).
* Practical Note: Given trilostane is available in 10mg, 30mg, 60mg, 120mg capsules, and it's difficult to split them accurately, you might need to start with the lowest practical dose (e.g., 10mg SID or 10mg every other day for very small dogs) and adjust based on monitoring. For a 9yo Poodle, a 10mg capsule once daily might be a practical starting point if BID is not feasible due to capsule size. However, if possible, compounding for accurate BID dosing is ideal. Let's assume ideal scenario for the recommendation.
Monitoring involves a combination of clinical assessment and laboratory tests.
| Monitoring Event | Timing
1. Differentiation of Pituitary-Dependent Hyperadrenocorticism (PDH) vs. Adrenal-Dependent Hyperadrenocorticism (ADH)
The primary methods for differentiation are:
* Abdominal Ultrasound:
* PDH: Typically presents with bilaterally symmetric adrenal glands that are normal to mildly enlarged. Rarely, one adrenal gland may appear slightly atrophied due to the influence of a pituitary tumor.
* ADH: Characterized by a unilateral adrenal mass (often >2 cm in diameter) with contralateral adrenal atrophy. This is due to the autonomous cortisol production from the tumor suppressing endogenous ACTH, leading to atrophy of the other adrenal gland.
* Endogenous ACTH (eACTH) Concentration:
* PDH: eACTH levels are typically normal to high, as the pituitary gland is overproducing ACTH.
* ADH: eACTH levels are low to undetectable, as the autonomous cortisol production from the adrenal tumor suppresses pituitary ACTH release via negative feedback.
2. Trilostane Dosing Protocol
* Starting Dose: For a Miniature Poodle, a common starting dose is 0.5-1 mg/kg orally BID (twice daily).
* Rationale for BID: Many specialists advocate for BID dosing from the outset. Studies suggest that BID administration provides more consistent cortisol suppression throughout the day, potentially leading to better clinical control and fewer "breakthrough" signs compared to SID dosing, especially in smaller breeds.
* Administration: Always administer trilostane with food, as this significantly improves absorption.
* Example: For a 5 kg Miniature Poodle:
* Starting at 0.5 mg/kg BID: 2.5 mg BID (using the smallest available capsule size, typically 10 mg, you might need to use a compounding pharmacy or consider 10 mg SID initially if BID is not feasible with available capsule sizes, then adjust).
* Starting at 1 mg/kg BID: 5 mg BID (again, compounding may be necessary depending on capsule sizes).
* Practical Note: Given trilostane is available in 10mg, 30mg, 60mg, 120mg capsules, and it's difficult to split them accurately, you might need to start with the lowest practical dose (e.g., 10mg SID or 10mg every other day for very small dogs) and adjust based on monitoring. For a 9yo Poodle, a 10mg capsule once daily might be a practical starting point if BID is not feasible due to capsule size. However, if possible, compounding for accurate BID dosing is ideal. Let's assume ideal scenario for the recommendation.
3. Monitoring Schedule with ACTH Stimulation Test
Monitoring involves a combination of clinical assessment and laboratory tests.
| Monitoring Event | Timing
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