SSPG titer is a diagnostic marker for adrenocortical adenoma in patients with non-functioning adrenal incidentaloma.

We analyzed insulin resistance-related clinical markers as well as imaging characteristics of adrenal masses in 11 patients with incidentally discovered adrenal tumors that were diagnosed as non-functioning according to the results of the 1 mg dexamethasone suppression test and then voluntarily resected. Histologic examination of the resected tumors revealed adrenocortical adenoma in eight patients, and non-cortical tumors: a myelolipoma. an endothelioma and an adrenal vascular cyst in three patients. All eight patients with adrenocortical adenoma exhibited insulin resistance as estimated by the steady-state plasma glucose (SSPG). The mean systolic blood pressure of the patients with adrenocortical adenoma was higher than that of the patients with non-cortical tumors, even though three of eight patients were normotensive. HOMA-R, EIRI on 75 g oGTT. diastolic blood pressure and serum triglyceride were not significantly different between the patients with adrenocortical adenomas and those with non-cortical tumors. Imaging characteristic such as tumor size, shape and heterogeneity in the mass did not distinguish these two groups either. These results suggest that the presence of insulin resistance estimated by SSPG may be a diagnostic marker for adrenocortical adenoma in patients with a non-functioning incidentaloma.