Effects of acth and posture on aldosterone metabolism in essential hypertension

Timed urinary excretions of aldosterone 18-oxo-conjugate (oxo-c, a renal metabolite) and tetrahydro-aldosterqne glucuronide (THA-g, a hepatic metabolite) in response to posture and an 8-h infusion of ACTH were measured in control subjects and in patients with stable and labile essential hypertension. In patients with labile and also those with stable hypertension, the mean 4-h excretion of oxo-c, with subjects in the recumbent posture, was significantly greater and that of THA-g slightly less than in controls, while during upright posture the excretion rate of oxo-c declined much more in patients with both types of hypertension man in controls. ACTH infusion caused a greater increase in oxo-c excretion and a lesser increase in THA-g excretion during the subsequent 24 h in those with stable hypertension than in controls. These findings suggest that hepatic metabolism of aldosterone is relatively lower in both stable and labile essential hypertension, as supported by evidence of increased plasma protein binding and a comparatively lower metabolic clearance rate of aldosterone in some subjects. Furthermore, these altered patterns of aldosterone metabolite excretion in both stable and labile essential hypertension suggest that they may be the forerunner of established hypertension.