Background: The optimal treatment of choice for ACTH-producing pituitary adenomas is their complete removal by the transsphenoidal surgical approach. ACTH-producing pituitary adrenomas are, however, often small in size not detectable with neuro-imaging techniques, which may result in difficulties during their surgical removal. With the advent of rapid methods for plasma ACTH measurement, a few neurosurgical centers introduced intra-operative plasma ACTH determinations in peripheral and central blood samples to help improve the outcome of pituitary surgery in patients with Cushing's disease.
Method: To evaluate the usefulness of this new method, we performed, under standardized conditions, intra-operative plasma ACTH measurements with a rapid immunochemiluminometric method at different stages of transsphenoidal pituitary surgery in 7 patients with Cushing's disease.
Findings: We found that from the beginning of anesthesia until the end of operation, ACTH concentrations in venous plasma were highly variable by both the rapid and the standard methods. In most cases the changes in venous plasma ACTH concentrations that occurred until the end of surgery failed to indicate the removal of the ACTH-producing pituitary adenoma. However, a more than 50% decrease of venous plasma ACTH concentrations by the rapid assay was observed 2 h after completion of the operation in all but one of the patients. As evidenced by a long-term hormonal and clinical remission, these changes in plasma ACTH levels in all patients were accompanied by a complete removal of the ACTH-producing pituitary adenoma.
Interpretation: These findings indicate a slow disappearance of ACTH from the circulation after a successful pituitary surgery in patients with Cushing's disease.