Editing Hypercortisolism (section)

== Hypothalamus-Pituitary-Adrenal (HPA) Axis ==

* '''Hypothalamus'''
** '''Produces corticotropin-releasing hormone (CRH)'''
* '''Corticotropin-releasing hormone (CRH)'''
** '''Function:'''
*** '''Acts on the corticotropic cells of the anterior pituitary to make ACTH'''
** '''Secretion'''
*** Under tight control of the hypothalamic suprachiasmatic nucleus
*** '''Follows circadian patterns.'''
**** '''The highest level of cortisol in healthy subjects is detected in the mornings, and the nadir is observed at approximately 11 PM.'''
***** Even small perturbations of this physiologic rhythm are considered pathologic
* '''ACTH'''
** '''Functions (2):'''
**# '''Stimulates production of glucocorticoids and androgens by the adrenal cortex'''
**# '''Plays a critical role in maintaining adrenal cortical vitality.'''
**#* '''Without ACTH''' (e.g., when its secretion is suppressed by exogenous steroid intake), '''all but the mineralocorticoid(aldosterone)-producing cells of the adrenal cortex atrophy'''
** '''Secretion:'''
*** Stimulated by (3):
***# CRH (most important)
***# Oxytocin
***# Vasopressin
* '''Glucocorticoids act on to the hypothalamus and pituitary to inhibit production of CRH and ACTH (negative feedback)'''
** '''Patients with hypercortisolism may be at higher risk for post-adrenalectomy adrenal insufficiency than patients with non-cortisol secreting adrenal pathologies, because functionality of the contralateral gland may be suppressed'''
* '''Stress, whether physiologic or psychologic, appears to be the most important variable in modulating activity of the HPA axis'''