A case of Cushing's Syndrome due to ectopic ACTH secreting pheochromocytoma with positive feedback glucocorticoid receptor and its in vitro analysis

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 29-49-Congenital Adrenal Hyperplasia & Ectopic Cushing's
Clinical
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-39
Seiichirou Higuchi*1, Ikki Sakuma1, Tomoko Takiguchi1, Naoko Hashimoto1, Akina Shiga1, Hidekazu Nagano1, Sawako Suzuki1, Hisashi Koide1, Tomohiko Yoshida1, Ichiro Tatsuno2, Koutaro Yokote1 and Tomoaki Tanaka1
1Chiba University Graduate School of Medicine, Chiba, Japan, 2Toho University Sakura Medical Center, Sakura-City, Japan
Introduction

Adrenal pheochrmocytoma (PCS) are catecholamine-(CA) secreting tumor arising from chromaffin cells, which originally derives from neural crests, of the adrenal medulla and it is also capable of secreting a variety of hormones such as corticotropin releasing hormone, corticotrophin and vasopressin as well as cytokines. Here we report a rare case of ectopic ACTH syndrome caused by a PCS that exhibited diabetic ketoacidosis with Cushing features. Importantly, in vivo and vitro analysis revealed that Cushing syndrome (CS) was pathophysiologically enhanced by a paradoxical response of ectopic ACTH secretion to glucocorticoids (GC) in a positive feedback loop via GR expression in tumor cells.

Case Reports

A 56-year-old female with severe clinical features of CS presented the impaired consciousness due to serious diabetic ketoacidosis and then was admitted to our hospital. Endocrinological investigation showed the ectopic ACTH production with high level of cortisol and revealed markedly elevated urinary catecholamine, leading to the diagnosis of PCS. Consistently, CT scan and magnetic resonance imaging displayed a 5.6 cm of left adrenal tumor and MIBG and FDG-PET represented abnormal accumulation in tumor. Interestingly, we found that ectopic ACTH secretion and CA production were blocked by metyrapone treatment, suggesting the possibility of positive feedback loop of ACTH and CA regulation by GC. Indeed, the administration of metyrapone and phentolamine drastically improved hormonal status and stabilized the general condition of patient. Thus, left adrenalectomy was performed safely under stabilized conditions and resulted in remission of CS and PCS completely.  

In vitro Analysis

Immunohistological analysis clarified that the tumor consists of functionally distinct two types of cells; one is chromogranin-positive cells, a major components of tumor, stained with tyrosine hydroxylase (TH) and PNMT. Another is minor population of ACTH-positive cells with negative staining of TH and PNMT. Notably, both cells are positive for GR staining. In addition, gene expression analysis of tumor tissue and primary culture cells confirmed the expression of POMC, TH, PNMT and GR mRNA and demonstrated that the dexamethasone treatment markedly increased the secretion of CA and ACTH in medium as well as induction of TH, PNMT and POMC mRNA.

Conclusion

Thus, we describe a case of ectopic ACTH syndrome associated with PCS caused by two different tumor cell linage, and positive feedback of glucocorticoid-inducible ACTH secretion may contribute to aggravate the patient’s condition.

Nothing to Disclose: SH, IS, TT, NH, AS, HN, SS, HK, TY, IT, KY, TT

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