[Equine Cushing syndrome (ECS). Case report, review of its diagnosis and therapy and substantial differences from Cushing syndrome in dogs].

Equine and canine Cushing's syndrome, both of which are the result of elevated cortisol levels, show some different pathogenetical and clinical features and require different therapeutical approaches. In older horses the equine Cushing's syndrome (ECS) is not uncommon. Nearly all cases result from excessive hormone production in cells of the pars intermedia of the pituitary. Besides elevated levels of adrenocorticotrope hormone (ACTH), high peripheral levels of pro-opiomelanocortin, beta-endorphines and alpha-melanocyte-stimulating hormone can be measured. In middle-aged and geriatric dogs, Cushing's syndrome is the most frequently diagnosed endocrinologic abnormality. 80-85% of cases are pituitary-dependent and 15-20% are caused by cortisol producing tumors of the adrenals. 90% of pituitary lesions can be identified as adenomas, which are localised in most cases in the pars distalis of the gland, but may occur rarely in the pars intermedia, too. Clinical symptoms in both species are characterised by wasting despite good appetite or polyphagia, reduction of muscle mass with altered fat deposition and lethargy. Whereas polydipsia/polyuria is a very common feature in dogs with Cushing's syndrome, in horses it is almost invariably a sign of concurrent secondary diabetes mellitus. A typical symptom in ECS is a continuously growing haircoat (hirsutism), whereas in canine Cushing's syndrome generalised alopecia may bring the owner to consult a veterinarian. The symptoms and diagnostic procedures in a 33-year-old mare are described. Useful diagnostic tests are reviewed with special attention to species differences in reacting to them. The therapeutic approach with dopamine-agonists such as bromocriptine and pergolide as well as cyproheptadine to ECS is reviewed.