The recent increasing use of ultrasound and computed tomography has revealed numbers of incidentally discovered adrenal tumors. Many studies have focused on their surgical management, but the biological characteristics of these adrenal tumors have remained unclear. Adrenal tumors were resected from 10 patients who underwent gastrectomy or cholecystectomy. No signs or symptoms of adrenal hormone excess or deficiency were evident either before or after the operation. Moreover, after surgery, no major differences in signs and symptoms including blood pressure levels were observed. Before surgery, neurogenic tumors and cysts were excluded by enhanced magnetic resonance imaging. Steroid contents and both the activities and amounts of steroidogenic cytochrome P-450s in the adrenocortical adenomas of these patients were examined. Microscopic examination revealed that the tumors were surrounded by a thin, non-intact capsule; the surrounding cortex was not atrophic and apparently normal; and the cells of both the tumor and adjacent portions were arranged in nests and cords. Measurements of all steroid content (pregnenolone, progesterone, corticosterone, 11-deoxycorticosterone, 18-hydroxydeoxycorticosterone, cortisol, and dehydroepiandrosterone) except aldosterone in 5 resected adrenal tumors were within the normal ranges for the adrenals of 5 patients with renal cell carcinoma. Aldosterone content in tumor portions was significantly lower than in the apparently normal adrenals. Although in both tumor and adjacent portions of another 5 resected adrenal tumors the activities and amounts of cytochrome P-450s (P-450scc, P-45011β, P-450aldo, P-45017αand P-450C21) Were Also Within The Normal Ranges, the Activities of P-450sccSand P-45011βin the Tumor Portion were greater than those in the adjacent portion. Grossly well-demarcated yellowish-brown tumors of the adrenal gland were observed in all the cases of adrenal tumor. The above results suggested that adrenal incidentalomas produce adrenal steroids through steroidogenic enzymes in both the tumor and adjacent portions. In addition, decreases in aldosterone content and increases in the activities of P-45017α in tumor portions suggest the shift of steroidogenesis from a mineralocorticoid pathway to a glucocorticoid pathway.
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