The hypothalamic-pituitary-adrenal axis and pathophysiology of hyperadrenocorticism

The hypothalamic-pituitary-adrenal axis consists of the hypothalamus and corticotropin-releasing hormone, the pituitary and corticotropin, and the adrenal cortex and glucocorticoid production. The clinical syndrome of hyperadrenocorticism results from glucocorticold excess. This steroid excess, in turn, may result from an adrenal tumor or more commonly from a pituitary tumor causing excessive corticotropin and consequently glucocorticoid excess, In dogs, such a pituitary tumor may arise from either the anterior or intermediate robes, suggesting that there are multiple causes for hyperadrenocorticism in this species.