Primary aldosteronism due to unilateral adrenal hyperplasia: report of two cases and review of the literature

Unilateral adrenal hyperplasia (UAH) is a rare, surgically correctable subset of primary aldosteronism (PA), which shows similar endocrine features to aldosterone-producing adenoma (APA). We report here two Japanese patients with UAH. Case 1 was a 62-year-old man with a four-year history of hypertension. Hypokalemia and suppressed plasma renin activity (PRA) with elevated plasma aldosterone concentration (PAC) were observed, while no adrenal nodules were identified by abdominal computed tomographic (CT) scan. Adrenal scintigraphy did not reveal definite localization. The selective adrenal-vein sampling for determinations of PAC showed an over-functioning left adrenal gland, and a left adrenalectomy was performed. Diffuse micronodular adrenocortical hyperplasia was observed. Case 2 was a 61-year-old man with a six-year history of hypertension. At the first visit to our hospital, hypokalemia and suppressed PRA with elevated PAC were observed. An abdominal CT scan showed a left adrenal mass 1.5 cm in diameter, while adrenal scintigraphy did not reveal definite laterality. A left adrenalectomy was performed, and three macronodules and diffuse micronodular adrenocortical hyperplasia were observed. Hypokalemia, hypertension and endocrine data became normal, and both patients have been well with no signs of recurrence for eight years (case 1) and seven months (case 2) after surgery. Clinical characteristics and endocrine features of UAH are also reviewed.