Cortisol responses to diazoxide in man and their possible relationship to effective blood volume

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In previously reported studies, oral salt loading resulted in increases in urinary cortisol and the cortisol secretion rate, and, conversely, the potent diuretics, hydrochlorothiazide or ethacrynic acid, resulted in decreased cortisol excretion. Because of its structural similarity to hydrochlorothiazide and also because it reduces the effective blood volume without inducing sodium depletion it seemed that diazoxide would be useful in further studies of the cortisol responses noted above. The administration of oral diazoxide, 200–400 mg./day, to five normal subjects resulted in evidences of diminished cortisol secretion in every instance; mild sodium retention was noted, although aldosterone excretion did not increase significantly except in one subject. The results of all these studies are consistent with the proposition that cortisol production increases with factors tending toward volume hyperexpansion and decreases with those tending to reduce the effective blood volume. It is tempting to speculate that these cortisol responses reflect another mechanism involved in the maintenance of volume homeostasis.