ACTH overexpressing pituitary hyperplasia in a patient with ectopic ACTH-syndrome due to carcinoid of the lung

Ectopic ACTH-syndrome is the most diagnostically challenging  variant of endogenous hypercortisolism. Particularly difficult differential diagnosis of this syndrome is from Cushing's disease (CD), as currently there is no single test sufficiently accurate to differentiate accurately ectopic ACTH production from the pituitary. The main functional tests are based on the fact that the vast majority of ectopic ACTH production is autonomous and suppresses one from pituitary. But in some cases this is not observed, and then the data obtained all necessary laboratory and instrumental research evidence in favor of central genesis of CD in a patient with ACTH ectopic secretion, which can lead to inappropriate treatment. If you confirm the ectopic ACTH-syndrome, it may take quite a long time of searching for the pathological focus, as there is no sufficiently precise imaging and diagnostic method for determining the localization of ectopic source of ACTH production. Thus, the differential diagnosis of ACTH-dependent hypercortisolism and localization of the ectopic tumor is the cornerstone of early and radical treatment of patients. We present a difficult clinical case of a patient having a pituitary hyperplasia with excessive ACTH expression with primary ectopic ACTH syndrome caused by lung carcinoid.