Cortisol binding capacity of corticosteroid binding globulin in hyperadrenocorticoid and healthy dogs.

Corticosteroid binding globulin (CBG) binding capacity and plasma cortisol concentration were determined in 27 dogs with hyperadrenocorticism and in 17 healthy control dogs. Cortisol concentrations were significantly higher in hyperadrenocorticoid dogs than in controls. CBG binding capacity did not differ between the two groups. It is concluded that excessive endogenous cortisol secretion does not induce an increase in CBG binding capacity. Consequently, the determination of CBG binding capacity provides no additional information for the diagnosis of canine Cushing's syndrome.