Reduced adrenal secretory mass after unilateral adrenalectomy for aldosterone-producing adenoma may explain unexpected incidence of hypotension.

In a prospective study of 37 patients who had unilateral adrenalectomy for an aldosterone-producing adenoma, five of 33 (15%) were symptomatically hypotensive after at least 1 year, and eight of 29 (28%) who were observed 3, 6, 12, 18 and 24 months after the operation showed 2-year blood pressures below the fifth percentile for age- and sex-matched controls. Postoperatively, plasma aldosterone was lower, and plasma renin activity higher than in controls, these differences being more marked in the hypotensive group. Pre-operatively elevated atrial natriuretic factor fell to levels lower than in controls. These serial changes in volume-regulatory hormones are consistent with chronic hypovolaemia, due to relative hypoaldosteronism. Plasma cortisol was lower 6 months after the operation and plasma adrenaline levels fell by half. A reduced adrenocortical (aldosterone and cortisol) and adrenomedullary (adrenaline) secretory mass may play a role in the hypotension observed after unilateral adrenalectomy.