Aldosterone Secretory and Glucocorticoid Excretory Responses to Alpha 1-24 ACTH (Cortrosyn) in Sodium-Depleted Normal Man

Five normal volunteers, ages 18–29 yr, were placed on a 10 mEq sodium/100 mEq potassium isocaloric constant diet. Two, four, seven and eleven units of α 1-24 ACTH (Cortrosyn®) were infused over 24 hr in 5% dextrose/water in a random sequence. Each study period consisted of three consecutive days of normal, upright, daytime posture followed by two days of supine posture. Cortrosyn® was infused on the second supine day. During the infusion of two units of Cortrosyn® over 24 hr, all subjects had significant increases in aldosterone secretion (p < 0.02) and urinary potassium excretion (p < 0.01). The maximum 17-hydroxycorticosteroid response in these subjects did not occur until at least seven units of Cortrosyn® were infused over 24 hr, indicating that ACTH stimulation of aldosterone secretion can occur at levels insufficient to produce maximal cortisol secretion. It is concluded that a dose of α 1-24 ACTH as low as 1.4 mU/min caused a significant stimulation of aldosterone secretion in sodium-depleted man. Dietary sensitization of adrenocortical responsiveness was likely since sodium restriction is known to enhance the aldosterone stimulating properties of ACTH.