67-year-old man presented with long-standing hypertension and osteoporosis with recurrent vertebral fractures.
Initial investigation revealed an elevated aldosterone renin ratio of 97 (aldosterone 680pmol/L, renin 7mU/L) with spontaneous hypokalaemia 3.3mmol/L. Dedicated CT adrenal found 19x19x13mm right adrenal adenoma with Hounsfield unit 1.0. Further biochemical assessment showed normal plasma metanephrines, and a non-suppressed 1mg dexamethasone suppression test (basal cortisol 602nmol/L, ACTH 6.6pmol/L and post cortisol 69nmol/L). 24hour urine free cortisol was normal at 171nmol/24hr, and serum DHEAS low at 1.0umol/L. A 2mg low dose dexamethasone suppression test found basal cortisol 581nmol/L and post cortisol 66nmol/L. Seated saline suppression test found baseline potassium 3.7mmol/L, cortisol 312 nmol/L and aldosterone 578pmol/L with 4-hour results showing potassium 3.1mmol/L, cortisol 707nmol/L and aldosterone 779pmol/L. He has been referred for adrenal vein sampling (AVS). Given the possibility that the adrenal adenoma may be coproducing aldosterone and cortisol, the use of plasma metanephrine to determine cannulation and lateralisation is planned.
It is becoming increasingly recognised that adrenal aldosterone-producing adenomas can co-secrete cortisol, with prevalence of 5-26% (1-4). In this group there are higher rates of cardiovascular complications, dysglycaemia and osteoporosis when compared to aldosterone-producing adenomas (1,5). The presence of hormonal co-secretion raises challenges with standard AVS interpretation, which relies on cortisol results for assessment of cannulation and lateralisation (6,7). Use of plasma metanephrine has been proposed as an alternative parameter to cortisol, and has been shown to be more reliable in cases of cortisol and aldosterone co-secretion (8-10). Adrenalectomy is recommended in cases where lateralisation is confirmed on AVS, however in patients with co-secretion of aldosterone and cortisol there are increased postoperative rates of glucocorticoid deficiency, which is typically transient (3).
We report on a case of a man with hyperaldosteronism with possible mild autonomous cortisol secretion (MACS), and discuss the diagnostic challenges.