Cushing's syndrome is a rare disease caused by chronic, excessive and inappropriate exposure to glucocorticoids. It is associated with increased incidence and prevalence of psychopathology (approximately 65%). The incidence of depressive episode is about 63% and of hypomanic or manic episode, 3%. In this paper, the author proposes to describe a case with evident psychopathological manifestations of a patient whom was diagnosed with Bipolar Disorder, mixed episode, due to Cushing's syndrome (secondary to pituitary adenoma), when decreased corticosteroid therapy. The remission was achieved not only with replacement doses of corticosteroids, but with the introduction of a mood stabilizer and anti-psychotic low dosage.