Dexamethasone-suppressible hyperaldosteronism. Adrenal transition cell hyperplasia?

Abstract

Dexamethasone-suppressible hyperaldosteronism is a rare familial syndrome in which hypokalemia, suppression of plasma renin concentration, and elevated aldosterone secretion are corrected by treatment with glucocorticoids. Regulation of adrenocortical function and body electrolytes was studied in two affected brothers. Both were hypertensive (210/128 and 160/106 mm Hg) with hypokalemia (3.3 and 3.5 mM) and low plasma renin concentrations. Aldosterone was elevated intermittently with levels as high as 45 ng/dl (normal range, 4-16 ng/dl). Cortisol concentrations were normal but were correlated with aldosterone levels (r=0.9 and 0.7). Concentrations of 11-deoxycorticosterone (19 and 21 ng/dl; normal range, 4-16 ng/dl) and 18-hydroxycortisol (1000 and 950 ng/dl; normal range, 34-150 ng/dl) were elevated, and diurnal changes in both were the same as those seen with aldosterone. Infusion of adrenocorticotropic hormone1-24 (ACTH) caused exaggerated increases of aldosterone, 11-deoxycorticosterone, and 18-hydroxycortisol; cortisol response was normal. A 4-week trial of dexamethasone normalized blood pressure and caused a natriuresis, a fall in aldosterone, and a rise in plasma renin. Administration of ACTH after dexamethasone treatment again caused exaggerated increases of aldosterone. Aldosterone did not respond to angiotensin II before dexamethasone therapy (r=0.01), but it showed a normal response after therapy (r=0.8, p<0.01). Neither administration of dopamine (1 μg/kg/min) nro long-term therapy with bromocriptine (2.5 mg t.i.d. for 4 weeks) affected aldosterone biosynthesis. Thus, loss of dopaminergic inhibition of mineralocorticoid biosynthesis does not account for hyperaldosteronism in this condition. The abnormal pattern of steroid secretion in these brothers is consistent with a population of adrenocortical transition-type cells that secrete aldosterone in response to ACTH but not to angiotensin II and have biosynthetic characteristics of both zona glomerulosa and zona fasciculata cell types. These properties would explain the excess synthesis of 18-hydroxycortisol from a cell type that can uniquely hydroxylate steroid at both the 17 and 18 positions.