Cushing's disease (hyperadrenocorticism) affects primarily middle-aged to senior dogs, with Poodles, Dachshunds, and Terriers overrepresented. Pituitary-dependent (PDH) accounts for 85-90% of cases; adrenal tumors for the rest. Use the Endocrinology Specialist and Bloodwork OCR for workup.
Signs: PU/PD, polyphagia, pot-bellied abdomen, muscle wasting, thin skin, alopecia, panting, lethargy. Often mistaken for "normal aging."
Screening: urine cortisol:creatinine ratio (UCCR)—if normal, Cushing's unlikely. If elevated, confirm with low-dose dexamethasone suppression (LDDS) or ACTH stimulation. LDDS differentiates PDH from adrenal tumor (cortisol suppresses at 8 hr in PDH). High-dose dexamethasone test or abdominal ultrasound further characterizes.
False positives occur with non-adrenal illness (stress, other disease). Always rule out concurrent conditions before diagnosing Cushing's. Diabetes and hypothyroidism can mimic or coexist.
Trilostane inhibits adrenal cortisol synthesis. Starting dose: 1-3 mg/kg PO BID with food. Recheck ACTH stimulation at 10-14 days, then 30 days, then every 3-6 months.
Target: post-ACTH cortisol 1.5-5.5 mcg/dL (or 2-6). Adjust dose based on results. Too high = inadequate control; too low = risk of hypoadrenocorticism.
Warning: Trilostane can cause hypoadrenocorticism (Addisonian crisis). Signs: lethargy, vomiting, collapse. If suspected, stop trilostane and give prednisone. ACTH stimulation confirms. Never start trilostane without baseline electrolytes.
- Cushing's: PU/PD, pot belly, hair loss—screen with UCCR, confirm LDDS.
- PDH 85-90%; adrenal tumor less common.
- Trilostane 1-3 mg/kg BID; recheck ACTH at 10-14 days.
- Target post-ACTH cortisol 1.5-5.5 mcg/dL.
- Monitor for hypoadrenocorticism; stop and give prednisone if crisis.