A correlative study between cortisol and ACTH in Cushing's disease following bilateral adrenalectomy and in Nelson's syndrome.

Correlation analysis was used to investigate the interrelation between plasma ACTH and serum cortisol concentrations determined at 8:00, 12:00, 16:00 and 22:00 h in 48 patients bilaterally adrenalectomized for Cushing's disease, including 23 patients with a pituitary adenoma (Nelson's syndrome). In the patients without evidence of a pituitary adenoma a significant inverse correlation was found at 8:00, 16:00, 22:00 h and additionally when all the pairs of estimations were analyzed. In a full-blown Nelson's syndrome an inverse correlation was not proved (p = 0.05). During remission in Nelson's syndrome an inverse correlation between cortisol and ACTH concentrations was stated at 8:00 h and after the evaluation of all the pairs of estimations. The results of our studies have shown that exogenous cortisol exerts a partial inhibitory action on ACTH secretion in patients bilaterally adrenalectomized for Cushing's disease. In active Nelson's syndrome this influence is questionable, it comes however into prominence during remission.