Ectopic ACTH syndrome: discrepancy between somatostatin receptor status in vivo and ex vivo, and between immunostaining and gene transcription for POMC and CRH

Abstract

Objective: To characterize somatostatin receptor status in vivo and ex vivo and immunoreactivity and gene transcription for proopiomelanocortin (POMC) and corticotropin-releasing hormone (CRH) in a case of Cushing's syndrome caused by a sporadic metastatic medullary thyroid carcinoma (MTC).

Methods: (111)In octreoscan, analysis of tumorous mRNA transcripts for somatostatin receptor subtypes (SSTR) as well as for POMC and CRH.

Results: The tissue was intensely positive by (111)In octreoscan but expressed only SSTR 1, 3 and 5. There was immunopositivity only for CRH, but gene transcription for both POMC and CRH was seen.

Conclusions: (1) This first comparison between somatostatin receptor status in vivo and ex vivo in MTC shows a marked positive octreoscan despite absent SSTR 2 expression, and (2) this is the first report of a discrepancy between immunostaining and gene transcription for POMC and CRH.