A bromocriptine-responsive corticotroph adenoma secreting alpha-MSH in a patient with Cushing's disease.

Clinical and in-vitro investigations have been performed on a corticotroph adenoma removed from a patient suffering from Cushing's disease. Prior to surgery, the patient's Cushing's disease had been successfully controlled, clinically and biochemically, by long term administration of bromocriptine. After selective adenomectomy, tumour tissue was investigated by a perfused isolated cell column technique. It was shown that the tumour cells secreted immunoreactive- (IR)- ACTH and IR-alpha-MSH and that the release of both peptides was promptly suppressed by dopamine. Chromatographic analysis of the secreted IR-alpha-MSH revealed a high proportion of acetylated alpha-MSH; smaller amounts of desacetyl alpha-MSH and diacetyl alpha-MSH were present. The relevance of these findings to the proposal that certain corticotroph adenomas are derived from the intermediate lobe of the pituitary is discussed. It is concluded that there is little direct evidence for involvement of the residual zona intermedia of the adult human pituitary in the development of Cushing's disease.