Histological and biochemical distinctiveness of atypical aldosterone‐producing adenomas responsive to upright posture and angiotensin

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Abstract
Fifteen patients with primary aldosteronism were classified as anglotensin II-unresponsive aldosterone-producing adenoma (All-U APA, n = 9), or anglotensin II-responsive aldosterone-producing adenoma (All-R APA, n= 6), based on the responsiveness of aldosterone to upright posture and to anglotensin II infusion. Lack of aldosterone response to anglotensin II Infusion immediately post-operatively In the All-R APA subtype was consistent with previous responsiveness residing solely within the adenoma. Cortisol levels In five of the six patients with All-R APA failed to suppress normally with dexamethasone consistent with some autonomous production of cortisol by the adenoma. In contrast, cortisol levels suppressed normally during dexamethasone administration In all patients with All-U APA. This biochemical distinction can be added to the previously described overproduction of 18-oxo cortisol in All-U APA but not in All-R APA. Histological examination of adenoma sections revealed predominantly (±-50%) zone fascicuiata type cells in All-U APA. In contrast, All-R APA contained less than 20% zona fasciculata type. Thus, biochemical differences between All-U APA and All-R APA subtypes of primary aldosteronism may be due to underlying differences In cellular composition of the aldosterone-producing adenomas.