RESUMO
Objective:To investigate the pathogenesis of Cushing′s syndrome induced by medullary thyroid carcinoma.Methods:Started from April 2011 to present, three medullary thyroid carcinoma patients with Cushing′s syndrome were enrolled in this study. All patients were 40 to 50 years old, one female and two males. The blood pressure, blood glucose, thyroid function and antibodies, calcitonin, and carcinoembryonic antigen(CEA)were detected. The qualitative and localized diagnosis of Cushing′s syndrome was performed by high- and low-dose dexamethasone suppression tests as well as imaging examinations. The biopsies of all patients were taken to test the immunostaining of calcitonin, adrenocorticotropin(ACTH), and corticotropin-releasing hormone(CRH).Results:According to the clinical manifestation and function tests, three patients were diagnosed as medullary thyroid carcinoma accompanied by ACTH-dependent Cushing′s syndrome. All patients showed positive immunohistochemical staining of calcitonin and CRH, with negative immunostaining of ACTH in one and positive immunostaining of ACTH in two patients. Therefore, the diagnosis of ectopic CRH syndrome caused by medullary thyroid carcinoma was definite.Conclusions:Medullary thyroid carcinoma is a rare cause of Cushing′s syndrome. Tumor cells secrete ACTH and CRH, which in turn cause hypercorticoremia. Ectopic CRH syndrome is very rare. Early diagnosis can be made by immunohistochemical staining of biopsy tissues to guide early targeted treatment and improve the prognosis.