Questions: Adrenal Steroid Hormones and the Stress Response

Question 1

A patient is injected with epinephrine (adrenaline) to treat a severe allergic reaction. Which structure produced this epinephrine in a healthy individual?

• A. The zona fasciculata of the adrenal cortex, as part of the HPA axis
• B. The zona glomerulosa of the adrenal cortex, which produces mineralocorticoids
• C. The adrenal medulla, which is derived from neural crest tissue and is part of the sympathetic nervous system
• D. The anterior pituitary, which produces epinephrine in response to ACTH

Answer: (C)

Epinephrine (adrenaline) is produced by the adrenal medulla, not the adrenal cortex. The medulla is derived from neural crest tissue and is functionally a modified sympathetic ganglion — its chromaffin cells are postganglionic neurons that release epinephrine directly into the bloodstream rather than onto a target organ. The adrenal cortex (the outer layer) produces steroid hormones: cortisol from the zona fasciculata and aldosterone from the zona glomerulosa. The two zones are structurally adjacent but functionally distinct: the medulla is part of the sympathetic nervous system while the cortex is part of the endocrine HPA axis.

Question 2

A clinician administers dexamethasone (a synthetic glucocorticoid) to a patient and finds that ACTH and cortisol levels do not fall. What does this indicate?

• A. The patient has Addison disease (cortisol deficiency), confirming that the adrenal cortex cannot produce cortisol
• B. The HPA axis negative feedback loop is broken — a hallmark of conditions like Cushing syndrome where autonomous cortisol or ACTH production bypasses feedback control
• C. The test is working correctly — ACTH and cortisol should not fall in response to dexamethasone
• D. The patient has a pituitary adenoma that secretes excess growth hormone, not ACTH

Answer: (B)

The dexamethasone suppression test exploits the HPA axis negative feedback: in a healthy individual, dexamethasone (a potent synthetic glucocorticoid) signals the hypothalamus and pituitary to suppress CRH and ACTH release, which causes endogenous cortisol to fall. Failure to suppress means the feedback loop is disrupted. This is the hallmark of Cushing syndrome, where an autonomous cortisol-secreting adrenal tumor, an ACTH-secreting pituitary adenoma, or ectopic ACTH production overrides the feedback signal. Addison disease would show low baseline cortisol with no need to suppress further.

Question 3

Epinephrine and cortisol are both produced by the adrenal cortex as part of the HPA axis stress response.

• T. True
• F. False

Answer: False

False. Epinephrine is produced by the adrenal medulla (derived from neural crest, part of the sympathetic nervous system), not the adrenal cortex. Cortisol is produced by the zona fasciculata of the adrenal cortex as the terminal product of the HPA axis (hypothalamus → CRH → pituitary → ACTH → adrenal cortex → cortisol). The two systems are anatomically adjacent and both respond to stress, but they are distinct in origin, mechanism, and timescale: epinephrine provides the immediate alarm response (seconds), while cortisol provides the sustained metabolic response (minutes to hours).

Question 4

Elevated cortisol inhibits both CRH release from the hypothalamus and ACTH release from the anterior pituitary, forming a negative feedback loop that prevents excessive HPA axis activation.

• T. True
• F. False

Answer: True

True. Cortisol acts at both levels of the HPA axis to shut down its own production: it suppresses CRH release from the hypothalamus and directly inhibits ACTH secretion from the anterior pituitary. This dual negative feedback ensures that the stress response is self-limiting — cortisol rises to address the metabolic demands of stress and then signals the axis to stand down. This feedback is so reliable that its integrity can be assessed clinically (dexamethasone suppression test): failure to suppress indicates loss of feedback control, as seen in various forms of Cushing syndrome.

Question 5

Why does the body need both epinephrine (from the adrenal medulla) and cortisol (from the adrenal cortex) during a stress response? What does each contribute that the other cannot?

Model answer: Epinephrine provides the immediate alarm response: within seconds, it increases heart rate and cardiac output, redirects blood flow from gut to muscle, dilates airways, and mobilizes glucose from glycogen — readying the body for immediate physical action. This fast response is mediated through membrane receptors (adrenergic receptors) and requires no gene transcription. Cortisol operates on a slower timescale (minutes to hours) and addresses the sustained metabolic demands of the stress response: it promotes gluconeogenesis (generating new glucose from amino acids and glycerol), breaks down muscle protein and fat to supply substrates, suppresses immune and inflammatory responses that would divert energy, and sensitizes the cardiovascular system to epinephrine. Cortisol essentially provides the logistics to sustain what epinephrine initiates — without cortisol, the fuel supply for a prolonged stress response would fail.

The complementarity of the two systems is illustrated by Addison disease (cortisol deficiency): patients can mount an initial fight-or-flight response via epinephrine, but they cannot sustain it metabolically and are dangerously vulnerable to even mild stressors. Cushing syndrome shows the opposite problem: chronic excess cortisol produces hyperglycemia, muscle wasting, and immune suppression even in the absence of acute stress — every effect of cortisol carried to a pathological extreme. Together, these conditions confirm that cortisol's role is not interchangeable with epinephrine's, and that each is necessary for a fully functional stress response.