Endocrine Disorder Practice Test

Primary adrenal insufficiency occurs when the adrenal cortex cannot produce enough cortisol. Since cortisol feeds back to suppress ACTH, a failing adrenals leads to a loss of cortisol and a compensatory rise in ACTH. So you get high ACTH with low cortisol, which is the classic pattern pointing to a problem at the adrenal gland itself rather than the pituitary or hypothalamus. If ACTH were low with low cortisol, that would suggest secondary adrenal insufficiency from pituitary/hypothalamic failure. If both ACTH and cortisol were high, that would indicate cortisol excess, not insufficiency. If ACTH were low with high cortisol, that would fit exogenous steroid effect or ACTH-independent Cushing syndrome, not Addison’s.