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

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.