• INCLUSION CRITERIA:

Patients with the following characteristics may be included in the protocol:

Age 18-75 years.

Evidence of Cushing syndrome. Evidence to suggest overactivity of the hypothalamic-pituitary-adrenal axis, such as increased urinary excretion of glucocorticoids or lack of suppressibility with low doses of dexamethasone in conjunction with clinical features, will be sought prior to admission.

EXCLUSION CRITERIA:

Patients will be excluded from entry to the protocol if:

A clear-cut pituitary tumor is present on T1-weighted conventional pituitary MR scan.

There is any contraindication to catheterization. Patients with known reaction to contrast material will be excluded from this elective study if they have a strong history of previous contrast media reaction and cannot be studied safely by giving medical prophylaxis before the procedure.

The patient is pregnant.

Combined blood withdrawal during the six weeks preceding the study exceeds 450 ml, or if hematocrit at entry is less than 33%.

Because of the increased risk of morbidity caused by contrast dyes in patients with a renal dysfunction, patients with a creatinine greater than 1.3 mg/dl will be excluded.

Patients with a diastolic blood pressure persistently greater than 100 mm Hg (with or without medication) will be excluded from sampling procedures.

They have had radiation exposure during the previous year that represents a significant additive risk in combination with the expected doses in this protocol. Patients and their doctors will be questioned about their exposure to radiation before they are accepted into the protocol.

For the questionnaire only, patients who do not speak and read English will be excluded. This instrument has not been validated in non-English speakers.