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Regulation of Aldosterone in the Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)

1974; Oxford University Press; Volume: 39; Issue: 1 Linguagem: Inglês

10.1210/jcem-39-1-136

1945-7197

Marshal Fichman, Andrew M. Michelakis, Richard Horton,

Birth, Development, and Health

The effect of antidiuretic hormone (ADH) and water retention on plasma renin (PRA) and aldosterone was studied in 4 cases of SIADH with serum sodium concentration less than 120 mEq/l and in 3 normal subjects given ADH and water. Plasma aldosterone was measured by a double isotope method and by radioimmunoassay and PRA by Boucher type bioassay. In patients with SIADH on 100 mEq Na+ diet, supine aldosterone was 2–7 ng/100 ml (normal 5.2 ± 1.8) (sd) and increased normally by 4–6-fold on standing without change in serum electrolytes or cortisol. There was a normal increase in aldosterone following pressor doses of angiotensin, ACTH, and spironolactone. On a 10 mEq Na+ diet, there was a 10-fold increase in aldosterone, without change in cortisol or potassium. In normal subjects given ADH and water, supine aldosterone was normal (4–6 ng/100 ml), increased with standing 4-fold when serum Na+ was <128 mEq/l and increased normally following angiotensin infusion. Supine PRA was low or undetectable in both SIADH and ADH treated normal subjects. Standing did not measurably increase PRA in SIADH, which also remained low in ADH treated normals despite normal increases in aldosterone. On 10 mEq Na+ diet for 5 days, PRA remained suppressed after standing, but aldosterone increased normally. With water restriction in SIADH, both PRA and aldosterone markedly increased. These results indicate: 1. Despite water retention and high urine Na+, plasma aldosterone is normal and responsive to endogenous and exogenous stimuli. 2. There appears to be a dissociation between PRA which is suppressed, and aldosterone in both SIADH- and ADH-treated normals, suggesting the presence of a control system other than reninangiotensin, serum Na+, serum K+ or ACTH for aldosterone in man.