Decreased secretion of cortisol and ACTH after oral clonidine administration in normal adults

Clonidine, a selective noradrenergic receptor agonist, has been shown to affect various hormones acutely. It increases growth hormone levels in animals and in human adults and children. The effect of clonidine upon ACTH and cortisol levels is not as clear, and both stimulatory and inhibitory effects have been reported. We found a significant decrease in plasma cortisol concentrations after a single oral dose of clonidine in 12 healthy adults; ACTH levels measured in six of our patients also decreased. No changes in FSH, LH, or prolactin were seen after oral clonidine. Our data are compatible with an inhibitory noradrenergic mechanism modulating ACTH and cortisol secretion in normal adults.