Factors predicting the duration of adrenal insufficiency in patients successfully treated for Cushing disease and nonmalignant primary adrenal Cushing syndrome. 
Successful treatment of Cushing syndrome causes transient or permanent adrenal insufficiency deriving from endogenous hypercortisolism-induced hypothalamus-pituitary-adrenal-axis suppression.  We analyzed pre-treatment factors potentially affecting the duration of adrenal insufficiency.  We conducted a retrospective analysis on patients successfully treated for Cushing disease (15 patients) who underwent transsphenoidal surgery, and nonmalignant primary adrenal Cushing syndrome (31 patients) who underwent unilateral adrenalectomy, divided into patients with overt primary adrenal Cushing syndrome (14 patients) and subclinical primary adrenal Cushing syndrome (17 patients).  Epidemiological data, medical history, and hormonal parameters depending on the etiology of hypercortisolism were collected and compared to the duration of adrenal insufficiency.  The median duration of follow-up after surgery for Cushing disease and primary adrenal Cushing syndrome was 70 and 48 months, respectively.  In the Cushing disease group, the median duration of adrenal insufficiency after transsphenoidal surgery was 15 months: younger age at diagnosis and longer duration of signs and symptoms of hypercortisolism before diagnosis and surgery were associated with longer duration of adrenal insufficiency.  The median duration of adrenal insufficiency was 6 months for subclinical primary adrenal Cushing syndrome and 18.5 months for overt primary adrenal Cushing syndrome.  The biochemical severity of hypercortisolism, the grade of hypothalamus-pituitary-adrenal-axis suppression, and treatment with ketoconazole before surgery accounted for longer duration of adrenal insufficiency.  In patients with Cushing disease, younger age and delayed diagnosis and treatment predict longer need for glucocorticoid replacement therapy after successful transsphenoidal surgery.  In patients with primary adrenal Cushing syndrome, the severity of hypercortisolism plays a primary role in influencing the duration of adrenal insufficiency after unilateral adrenalectomy.