Demonstration of pro-opiomelanocortin mRNA in pituitary adenomas and para-adenomatous gland in Cushing's disease and Nelson's syndrome

Proopiomelanocortin, glucocorticoid, and CRH receptor expression in human ACTH-secreting pituitary adenomas

ACTH-secreting pituitary tumors are by definition partially autonomous, i.e., secrete ACTH independent of physiological control. However, only few, small-sized studies on proopiomelanocortin (POMC) and its regulation by corticotropin-releasing hormone (CRH) or glucocorticoids are available. Objective of the present study was to report on constitutive and CRH- and dexamethasone-regulated POMC, CRH (CRH-R1), and glucocorticoid receptor (NR3C1) gene expression in a large series of human corticotrope adenomas. Fifty-three ACTH-secreting adenomas were incubated with 10 nM CRH or 10 nM dexamethasone for 24 h. POMC, CRH-R1, NR3C1, and its alpha and beta isoforms were quantified and medium ACTH measured. Constitutive POMC expression proved extremely variable, with macroadenomas exhibiting higher levels than microadenomas. POMC increased during CRH in most specimens; conversely, changes induced by dexamethasone were varied, ranging from decrease to paradoxical increase. No correlation between POMC and ACTH was detected in any experimental condition. CRH-R1 expression was not linked to the response to CRH while NR3C1 was expressed at greater levels in specimens who failed to inhibit during dexamethasone; glucocorticoid receptor α was the more abundant isoform and subject to down-regulation by dexamethasone. Our results demonstrate a considerable variability in POMC expression among tumors and no correlation between POMC and ACTH, suggesting that POMC peptide processing/transport plays a major role in modulating ACTH secretion. Further, CRH-R1 and NR3C1 expression were not linked to the expected ligand-induced outcome, indicating that receptor signaling rather than abundance determines corticotrope responses. Our findings pave the way to new avenues of research into Cushing's disease pathophysiology.

Crooke's cell adenoma of the pituitary: an aggressive variant of corticotroph adenoma

Cushing's disease is caused by functional corticotroph adenomas of the pituitary, mostly noninvasive microadenomas. Classic Crooke's cells are nonneoplastic corticotrophs with cytoplasmic accumulation of cytokeratin filaments in response to glucocorticoid excess. Corticotroph adenomas exhibiting Crooke's change are rare and incompletely understood. We intend to define more clearly the clinicopathological features of Crooke's cell adenomas (CCA). Thirty-six CCAs were retrieved from the files of Mayo Clinic and from our (B.W.S., K.K.) consultation files. The number of informative cases varied for different criteria. Clinical follow-up was obtained in 31 cases. The 27 females and 9 males were 18 to 81 years of age (mean 46 years). At presentation, Cushing's disease was evident in 22/34 (65%); 81% were macroadenomas and 72% were invasive. All were initially treated by transsphenoidal resection. Twenty-five patients were followed for more than 1 year (mean 6.7 years). Of these, 15 (60%) developed recurrent tumor, and 6 (24%) had multiple recurrences. Lastly, 3 of these 25 patients (12%) died of tumor: 1 after multiple local recurrences and 2 from pituitary carcinoma. Compared with typical corticotroph adenomas, CCAs are aggressive. Most are functional adenomas occurring in middle-aged women and are invasive macroadenomas prone to recurrence. Morbidity and mortality rates are substantial. CCAs represent a distinct entity that should be separated from corticotroph adenomas without Crooke's hyaline change.

Absence of peritumoral Crooke's change is associated with recurrence in surgically treated Cushing's disease

BACKGROUND

Pituitary surgery is the standard treatment for Cushing's disease but is complicated by a recurrence rate that ranges from 5.9 to 27%. Whereas some recurrences may be due to technical or anatomical factors resulting in subtotal resection of adenoma, clinical relapse after total tumor resection is a well-documented occurrence. The factors leading to such recurrences are unknown.

METHODS

With the hypothesis that the pathology of the nontumoral adenohypophysis is important in predicting relapse, we undertook a study to determine if the absence of Crooke's change (CC), thought to be an indicator of nontumoral corticotroph inhibition, was associated with unexpected clinical recurrence. Twenty-one patients with Cushing's disease, with gross total resection of intrasellar corticotroph microadenoma, were reviewed independently by 2 neuropathologists for the presence of CC in adjacent adenohypophysis. All tumors were stained with H&E, PAS/orange-G and immunohistochemistry for ACTH. Clinical relapse was determined by chart reviews and defined as serum ACTH > 15 pg/ml, clinically Cushingoid, and/or radiographic evidence of recurrent tumor.

RESULTS

Seven of 21 patients recurred; 3 did not have CC in their initial resection specimen. All 3 of these patients had unexpected recurrences at 6 to 48 months post-op. Two patients with CC recurred at one year follow-up, 1 after 4 years and 1 after 5 years. All specimens from patients with long-term cure (follow-up from 9-72 months) contained CC. In this study, the absence of CC in peritumoral adenohypophysis was associated with unexpected recurrence of Cushing's disease (p = 0.0214).

CONCLUSIONS

We conclude that absence of CC in peritumoral adenohypophysis may be of some assistance in predicting recurrence of Cushing's disease after adequate resection of intrasellar microadenoma.