Serum Matrix Metalloproteinase-9 Levels in the Diagnosis of Functioning Adrena Tumors

Abstract

To investigate whether serum matrix metalloproteinase-9 (MMP-9) levels can be used as a diagnostic tool in determining the functioning status of benign adrenal tumors. In this case-control study, medical records of patients with adrenal tumors who consecutively presented to an endocrinology clinic between August 2005 and October 2008 were evaluated. Operation was recommended when the incidentaloma was larger than 4 cm or when a hypersecreting tumor was suspected. A control group of healthy persons matched for age, body mass index, and sex was also enrolled. Patients underwent routine endocrinologic examinations. MMP-9 levels were compared preoperatively and postoperatively. Findings were compared among patients with functioning adrenal tumors, patients with nonfunctioning adrenal tumors, and control participants. Of 370 patients with adrenal tumors, 50 with adrenal incidentaloma met the inclusion criteria. Twenty-five healthy individuals were enrolled as controls. Group 1 included 20 patients with functioning adrenal tumors (14 with Cushing syndrome and 6 with pheochromocytoma), and Group 2 included 30 patients with nonfunctioning adrenal tumors. MMP-9 levels were higher in patients with nonfunctioning adrenal tumors and functioning adrenal tumors than in control participants (P<.001). MMP-9 levels in patients with functioning adrenal tumors were significantly higher than those in patients with nonfunctioning adrenal tumors (P = .002). After operation, MMP-9 levels decreased significantly in patients with Cushing syndrome and in those with pheochromocytoma; however, patients with Cushing syndrome and pheochromocytoma had similar MMP-9 levels preoperatively and postoperatively. No significant linear correlation existed between tumor volume and MMP-9 levels. A significant positive correlation was determined between preoperative MMP-9 concentrations and 24-hour urinary fractionated metanephrine and epinephrine (r = 0.938, P = .006; r = 0.965, P = .002, respectively), between MMP-9 levels and baseline cortisol levels (r = 0.402, P = .003), and between MMP-9 levels and cortisol levels obtained after dexamethasone suppression testing (r = 0.357, P = .006). Our data suggest that serum MMP-9 levels may be useful in differentiating benign subclinical functioning adrenal tumors from benign nonfunctioning adrenal tumors.