Paradoxical response to dexamethasone in the diagnosis of primary pigmented nodular adrenocortical disease

Background: Primary pigmented nodular adrenocortical disease causes the Gus hing syndrome in children and young adults and is most frequently associate d with the Carney complex. Objective: To evaluate diagnostic tests for primary pigmented nodular adren ocortical disease. Design: Retrospective cohort study. Setting: Tertiary care center. Patients: 21 patients with primary pigmented nodular adrenocortical disease . The control groups consisted of 9 patients with macronodular adrenocortic al disease and 15 patients with primary unilateral adrenocortical disease ( single adenomas). Measurements: Clinical characteristics, radiologic imaging, and a 6-day Lid dle test with determination of urinary free cortisol and 17-hydroxycorticos teroid excretion. Results: Adrenal imaging and other tests were of limited value for the diag nosis of primary pigmented nodular adrenocortical disease. The Liddle test, however, distinguished patients with this disorder from those with other p rimary adrenocortical lesions. An increase of 50% or more in urinary free c ortisol levels on day 6 of the Liddle test identified 9 of 13 patients (69. 2% [95% Cl, 46.6% to 91.8%]) with primary pigmented nodular adrenocortical disease, excluded all patients with macronodular adrenocortical disease, an d was present in only 3 of the 15 patients with single adrenocortical adeno mas (20% [Cl, 0% to 40.2%]). An increase in urinary free cortisol excretion of 100% or more on day 6 of the Liddle test identified only patients with primary pigmented nodular adrenocortical disease. Conclusions: Patients with primary pigmented nodular adrenocortical disease responded to dexamethasone with a paradoxical increase in glucocorticoid e xcretion during the Liddle test. This feature distinguishes such patients f rom those who have the Gushing syndrome caused by other primary adrenal dis orders and may lead to timely detection of the Carney complex (a potentiall y fatal disorder) in asymptomatic patients.