Cushing's Disease
Cushing's disease (hyperadrenocorticism) results from chronic excessive cortisol production. The most common form (85%) is pituitary-dependent, caused by a pituitary tumor producing excess ACTH. Adrenal-dependent Cushing's (15%) results from an adrenal tumor. Iatrogenic Cushing's occurs from prolonged corticosteroid administration.
Symptoms & Signs
- Increased thirst and urination
- Increased appetite
- Pot-bellied appearance
- Hair loss (bilateral, symmetrical)
- Thin skin
- Recurrent skin infections
- Panting
- Muscle weakness
- Calcinosis cutis
Causes & Risk Factors
Pituitary-dependent (85%): pituitary adenoma producing excess ACTH. Adrenal-dependent (15%): adrenal adenoma or carcinoma producing cortisol autonomously. Iatrogenic: chronic exogenous corticosteroid administration.
Diagnosis
Screening tests: urine cortisol:creatinine ratio, low-dose dexamethasone suppression test, ACTH stimulation test. Differentiating tests: high-dose dexamethasone suppression, endogenous ACTH level. Abdominal ultrasound and MRI for tumor localization.
Treatment
Pituitary-dependent: trilostane (Vetoryl) or mitotane (Lysodren). Adrenal tumors: surgical adrenalectomy if no metastasis. Iatrogenic: gradual corticosteroid tapering. Radiation therapy for large pituitary tumors.
Prevention
Judicious use of corticosteroids (lowest effective dose, shortest duration). No prevention for spontaneous forms. Regular monitoring of dogs on chronic corticosteroid therapy.
Prognosis
Pituitary-dependent with treatment: median survival 2-2.5 years. Adrenal adenoma with successful surgery: good. Adrenal carcinoma: guarded. Quality of life typically improves significantly with treatment.