Inability of adrenal glands to generate enough glucocorticoids +/- mineralocorticoids for the body's needs.

Symptoms include weakness, fatigue, orthostatic hypotension, muscle aches, weight loss, GI disturbances, sugar and/or salt craving.

Diagnosis:- Measurement of serum electrolytes, morning/random serum cortisol and ACTH→ low cortisol, high ACTH in 1° adrenal insufficiency→ low cortisol, low ACTH in 2°/3° adrenal insufficiency due to pituitary/hypothalamic disease, and response to ACTH stimulation test- Alternatively, can use metyrapone stimulation test: metyrapone blocks last step of cortisol synthesis (11-deoxycortisol → cortisol). Normal response is ↓ cortisol and compensatory ↑ ACTH and 11-deoxycortisol. → In 1° adrenal insufficiency, ACTH is ↑ but 11-deoxycortisol remains ↓ after test. → In 2°/3° adrenal insufficiency, both ACTH and 11-deoxycortisol remain ↓ after test.