DIAGNOSIS AND TREATMENT OF NATURALLY-OCCURRING HYPOADRENOCORTICISM IN42 DOGS

Hypoadrenocorticism was diagnosed in 42 dogs over a two-and-a-half-yea r period. The disease occurred more commonly in young to middle-aged d ogs, with a female:male ratio of 2:1. Most dogs had chronic intermitte nt signs (eg, poor appetite, lethargy and vomiting), but more than a t hird were in acute adrenal crisis at the time of diagnosis. Serum bioc hemical testing revealed azotaemia, hyperphosphataemia, hyperkalaemia and hyponatraemia in almost all the dogs. In all dogs, results of adre nocorticotrophic hormone (ACTH) stimulation testing revealed a low to low-normal serum baseline cortisol concentration that failed to increa se after ACTH administration. In two dogs with persistently normal ser um electrolytes concentration, one had a markedly high plasma ACTH con centration diagnostic for primary hypoadrenocorticism, whereas the oth er had a low concentration confirming secondary hypoadrenocorticism. F ludrocortisone acetate was initially used for mineralocorticoid replac ement in 33 of the 37 treated dogs with primary hypoadrenocorticism (f inal median dosage, 27.0 mu g/kg/day), but supplementation was changed to desoxycorticos terone pivalate (DOCP) in four dogs because of poor response or adverse effects. Seven dogs with primary hypoadrenocortic ism were treated with DOCP (final median dosage, 2. 02 mg/kg/month). P rednisone, initially administered to 36 dogs; tvas discontinued in 11 dogs because of,side effects. Of Che dogs treated with fludrocortisone , tile response was considered good to excellent in 26 dogs (78.8 per cent), fair in three, and poor in four. All dogs treated with DOCP res ponded well.