Combined primary aldosteronism and preclinical Cushing's syndrome: an unusual case presentation of adrenal adenoma

A 55-year-old woman was referred to our institution for evaluation of elevated plasma creatine phosphokinase, hypokalemia and hypertension. Her chief complaints were muscle weakness and polyuria. A left adrenal mass, 4 cm in diameter, was noted on computed tomography. Hormonal assessment demonstrated markedly elevated plasma aldosterone concentration, markedly low plasma renin activity, an abnormal diurnal variation in serum cortisol levels, suppressed baseline plasma adrenocorticotrophic hormone, and nonsuppression of serum cortisol by dexamethasone suppression test. She showed no symptoms or signs suggestive of Cushing's syndrome. Adrenal scintigraphy with I-131-6-beta -iodomethyl-norcholesterol showed uptake on the left adrenal and inhibition of the contralateral adrenal gland. She was diagnosed with combined primary aldosteronism and preclinical Cushing's syndrome. Cases of combined primary aldosteronism and preclinical Cushing's syndrome are extremely rare. In patients with large aldosterone-producing adenoma, contralateral adrenal insufficiency should be anticipated after the removal of the tumor.