Inhibitory effect of ascorbic acid (vitamin C) on cortisol secretion following adrenal stimulation in children.

Measurements of plasma cortisol values before and at 4 and 6 hours after intramuscular administration of a depot preparation of synthetic b1-24 corticotrophin were carried out in 12 healthy children (group B) before, as well as on the 5th day of continuous ascorbic acid (AA) administration (1 g t.i.d. orally). Comparison of the results in group B with those of 8 healthy children similarly treated with corticotrophin but not given AA (group A) showed that, on the 5th day of AA administration the mean cortisol values after ACTH were significantly lower than the corresponding values in group A (p less than 0.02), or the post-ACTH values in group B observed on the 1st experimental day, i.e., before AA administration (p less than 0.001). On the other hand, AA administration had no significant effect on the fasting plasma cortisol values. These data suggest that AA excess following adrenal stimulation with ACTH exerts an inhibitory effect on cortisol secretion and consequently it may be of no benefit in conditions of stress.