Adrenal vs Pituitary
Primary adrenal insufficiency
(ai) is when the part of the adrenal glands which make cortisol is damaged so that cortisol is not produced in sufficient amount.
Acth from the pituitary gland is high. Skin bronzing may be seen. Secondary ai occurs when the pituitary gland isn't able to produce enough acth to signal the adrenals to make cortisol. Therefore, both acth and cortisol levels are low.