The prevalence of adrenal tumors is 1.4% in the general adult population and increases with patient age, according to a study published in the Annals of Internal Medicine. Researchers examined the prevalence and characteristics of adrenal tumors in an unselected screening population of 25,356 participants. Among participants, 351 had adrenal tumors, and prevalence increased with age, from 0.2% to 3.2% among those aged 18-25 and those older than 65, respectively. Overall, 337 of 351 participants with adrenal tumors were diagnosed with an adrenocortical adenoma, while 14 were diagnosed with another benign nodule and none had a malignant mass. Of 212 participants with an adenoma who completed endocrine testing, 69.3%, 18.9%, and 11.8% were diagnosed with a nonfunctioning adenoma, cortisol autonomy, and primary aldosteronism, respectively, and none had pheochromocytoma. The percentage of nonfunctioning adenomas was similar across age groups.