Distinguish adrenal failure from deficient ACTH, interpret cortisol testing in context, and connect daily replacement with practical adrenal crisis prevention.
A patient with weight loss, nausea, orthostatic dizziness, and low sodium may have adrenal insufficiency even when potassium is normal and the skin has not darkened. The first decision is whether the patient is stable enough for diagnostic testing. Shock, repeated vomiting, hypoglycemia, or altered consciousness makes treatment urgent.
Cortisol deficiency and aldosterone deficiency overlap in primary adrenal disease, but they are separate physiological problems. Use cortisol and ACTH to locate the cortisol defect; use blood pressure, potassium, renin, and aldosterone to assess mineralocorticoid function.
Two control systems share one adrenal cortex
Hypothalamic CRH stimulates pituitary ACTH, which supports cortisol production in the zona fasciculata. Cortisol restrains CRH and ACTH through negative feedback. Its normal daily rhythm produces higher concentrations near waking, and illness increases the demand. Cortisol supports vascular responsiveness to catecholamines, glucose availability, and appropriate regulation of inflammation. Deficiency can therefore produce hypotension, fatigue, abdominal symptoms, and hypoglycemia, especially in children. [1]
Locate the missing signal, then ask whether salt conservation is also impaired.
Reduced effective circulating volume: renin and angiotensin II or increased potassium ↓ Adrenal glomerulosa: aldosterone ↓ Renal sodium retention and potassium secretion
ACTH has a smaller acute influence; it is not the principal sustained regulator.
These are functional pathways, not a scale drawing. A pituitary cortisol defect can coexist with preserved aldosterone because the dominant control systems differ.
Primary adrenal insufficiency originates in the adrenal cortex. Low cortisol removes feedback, so ACTH rises. Aldosterone often falls as cortical disease progresses, with increased renin, renal sodium loss, potassium retention, and volume depletion. Secondary insufficiency results from deficient pituitary ACTH; tertiary insufficiency includes hypothalamic suppression after exogenous glucocorticoids. Both central forms usually preserve aldosterone. Normal potassium therefore helps explain a central pattern but does not rule out primary disease. [1][2]
ACTH is derived from proopiomelanocortin. Sustained excess ACTH-related melanocortin activity can darken palmar creases, scars, and oral mucosa in primary disease. Pigmentation is neither required for diagnosis nor unique to adrenal insufficiency: other ACTH-excess states can also cause it. Hyponatremia can occur in either primary or central disease because cortisol deficiency impairs free-water excretion, in part through increased vasopressin. Primary disease adds renal salt loss when aldosterone is deficient.
Try it here · Checkpoint 1 of 3
Make your prediction before reading the choices. A first attempt is just a starting point.
Case 2
Show answer and explanations for case 2
A. Renin-angiotensin and potassium regulation preserve aldosterone in central ACTH deficiency. (Best answer)
Central ACTH deficiency mainly affects cortisol; the dominant aldosterone regulators remain functional.
B. ACTH contributes enough chronic aldosterone stimulation to preserve potassium balance in central ACTH deficiency. (Why this does not fit)
ACTH is not the main sustained regulator of aldosterone; renin-angiotensin and potassium explain preservation better.
C. Potassium is chiefly controlled by pituitary vasopressin. (Why this does not fit)
Vasopressin chiefly regulates water handling. Renin-angiotensin signaling and potassium itself are the important sustained regulators of aldosterone.
D. Renal potassium wasting from cortisol deficiency offsets aldosterone loss. (Why this does not fit)
Central cortisol deficiency usually preserves aldosterone because its principal regulators remain intact; an offsetting renal potassium-wasting mechanism is not needed.
Takeaway: Preserved aldosterone is a functional distinction between central and many primary cases.
Find the cause without turning patterns into absolutes
Autoimmune adrenalitis is a major cause of primary disease in many higher-income settings. Test for 21-hydroxylase antibodies when appropriate and look for associated autoimmune thyroid disease, type 1 diabetes, or other features of autoimmune polyglandular syndromes. Tuberculosis and other infections, metastatic or infiltrative disease, bilateral adrenal hemorrhage, and adrenal surgery are additional causes. Their relative frequency depends on the population; tuberculosis is not a universal leading cause. [1][6]
Salt craving, weight loss, orthostatic hypotension, hyperpigmentation, and high potassium together strongly support primary disease. Early or partial disease may lack several of these features. A low cortisol with markedly elevated ACTH is more informative for localization than any single symptom. Aldosterone status must still be measured rather than inferred solely from a potassium result.
Central disease may follow pituitary surgery, radiation, a sellar mass, pituitary apoplexy, or postpartum pituitary injury after severe hemorrhage. Ask about other pituitary functions: failure to lactate, amenorrhea, reduced libido, headache, or visual symptoms can place a cortisol deficit in a wider syndrome. Sudden severe headache with visual loss and hypotension requires emergency assessment for apoplexy. Low free T4 with an inappropriately low or normal TSH supports central hypothyroidism; establish adrenal coverage before giving thyroid hormone when cortisol deficiency is possible. [3]
Exogenous glucocorticoids suppress CRH and ACTH. The exposure history includes tablets, injections, inhaled or topical products, and combinations of formulations. Strong CYP3A4 inhibitors can increase systemic exposure to some steroids. Longstanding ACTH deprivation can cause adrenal atrophy, so a chronically suppressed gland may respond poorly to cosyntropin. Conversely, recent pituitary injury can leave enough adrenal reserve for an initially reassuring stimulation response.
Neither result should be interpreted without the timing of the injury. Enzyme-inducing drugs such as rifampicin and phenytoin can accelerate cortisol metabolism and increase replacement requirements in a patient with limited adrenal reserve. Review new medicines and reassess replacement clinically; this does not justify a fixed dose increase for every interaction. [9][2][3]
Test the axis when the patient is stable
For a stable patient, obtain an early-morning cortisol with ACTH before starting replacement when this is safe. A random cortisol is difficult to interpret because of circadian variation and stress. In suspected central insufficiency, the Endocrine Society guideline uses an 8-9 AM cortisol below 3 micrograms/dL as strongly supportive and above 15 as likely excluding deficiency; intermediate results require further evaluation. These are clinical decision ranges, not universal assay-independent truths. Oral estrogen, pregnancy, low binding proteins, and recent steroid exposure can alter total-cortisol interpretation. [3]
The standard cosyntropin test administers 250 micrograms of synthetic ACTH, then measures cortisol at specified laboratory time points, commonly 30 and/or 60 minutes. The historical peak threshold of 18 micrograms/dL was established with older assays. Some modern assays require lower thresholds, often around 14-15 micrograms/dL, with timing-specific and platform-specific validation. Use the laboratory's validated threshold instead of diagnosing failure from an obsolete cutoff. A primary study comparing assays demonstrates why the same specimen can be classified differently by method. [1][4]
Once cortisol deficiency is established, an ACTH more than twice the assay's upper reference limit supports primary disease. Measure renin and aldosterone to evaluate mineralocorticoid deficiency. Antibody testing and, when indicated, adrenal imaging investigate the cause. Central disease calls for assessment of other pituitary axes and appropriate imaging. Tests performed after hydrocortisone or cross-reacting steroids may be uninterpretable; plan the interval and safety cover with the treating team rather than asking the patient to stop essential treatment unsupervised.
In suspected crisis, draw cortisol and ACTH if this can be done immediately, then treat. Do not delay hydrocortisone for a stimulation test, an imaging appointment, or an attempt to preserve a cleaner assay. Dexamethasone has less cortisol-assay interference in many methods but is not the preferred routine crisis steroid. [1][5]
Try it here · Checkpoint 2 of 3
Make your prediction before reading the choices. A first attempt is just a starting point.
Case 13
Show answer and explanations for case 13
A. The stimulation test identifies the cause of the patient's symptoms. (Why this does not fit)
The test assesses adrenal response to ACTH. Meeting its assay-specific threshold neither identifies a symptom cause nor evaluates all endocrine disorders.
B. It excludes every recent pituitary injury regardless of timing. (Why this does not fit)
An early central defect can retain a stimulation response, so context still matters.
C. It must be abnormal because every assay requires at least 18. (Why this does not fit)
Modern assays can have lower validated thresholds.
D. It meets this laboratory's biochemical response threshold; integrate timing and clinical context. (Best answer)
Using the validated assay-specific threshold avoids a false diagnosis based on the historical 18 cutoff.
Takeaway: Use the assay and sampling-time standard that generated the result.
Typical adult maintenance hydrocortisone replacement is 15-25 mg daily in two or three divided doses, with the largest dose on waking. This is a starting framework; body size, symptoms, interacting medicines, and clinical response guide individual care. Excess replacement can cause weight gain, hypertension, hyperglycemia, bruising, and bone loss. Inadequate replacement can leave fatigue, nausea, postural symptoms, or weight loss. Do not escalate treatment simply to normalize ACTH: achieving that biochemical target can require harmful glucocorticoid excess. [1]
Primary disease with confirmed aldosterone deficiency also needs fludrocortisone, often starting at 50-100 micrograms daily in adults. Follow postural symptoms, blood pressure, edema, electrolytes, and renin. Persistent salt craving, orthostasis, high potassium, and elevated renin suggest inadequate mineralocorticoid effect, after considering adherence and other causes. Hypertension with suppressed renin or edema suggests excess. Central and glucocorticoid-induced insufficiency generally do not require fludrocortisone because aldosterone regulation is preserved. [1][2]
Stress dosing should be written down before illness occurs. A febrile illness with reliable oral intake often requires a temporary oral increase; high fever may require a larger increase. Persistent vomiting, severe diarrhea, hemodynamic instability, major surgery, or inability to absorb tablets requires parenteral coverage. A single instruction to triple every dose for every kind of stress is inadequate. Patients and a chosen support person need practical injection training, an emergency supply, and a steroid emergency card or medical alert identification. [1][5]
For glucocorticoid-induced suppression, a taper is appropriate only when the treated inflammatory disease is controlled and steroid therapy is no longer needed. Courses shorter than 3-4 weeks generally do not require tapering solely to prevent adrenal insufficiency. Longer exposure above physiological doses carries more risk. Near a physiological dose, morning cortisol can help assess recovery: the 2024 guideline uses above 10 micrograms/dL as supporting recovery, 5-10 as a reason to continue physiological cover and repeat later, and below 5 as a reason to continue and reassess after a longer interval.
These recovery thresholds answer a different question from the initial diagnosis of pituitary disease. [2]
Restore circulation while replacing the missing stress response
Suspect adrenal crisis in a patient with known or possible insufficiency who develops shock, severe weakness, vomiting, abdominal pain, confusion, or hypoglycemia. Infection, missed replacement, abrupt steroid withdrawal, and surgery are common precipitating situations. In an adult, give hydrocortisone 100 mg intravenously or intramuscularly immediately, followed by 200 mg over 24 hours by infusion or 50 mg every six hours. Provide isotonic crystalloid promptly, reassessing volume tolerance, and give dextrose for hypoglycemia. Pediatric doses are age or body-surface-area based and should follow a pediatric emergency protocol. [1][5]
Monitor glucose, sodium, potassium, renal function, urine output, and circulation while treating the precipitant. High stress doses of hydrocortisone provide substantial mineralocorticoid activity; fludrocortisone is usually unnecessary during this phase and is resumed when glucocorticoid doses return toward maintenance in primary disease. Severe hyperkalemia requires urgent potassium-lowering treatment and monitoring; toxic electrocardiographic changes also require intravenous calcium for cardiac protection. Insulin with glucose shifts potassium into cells, with subsequent glucose monitoring. [8] Steroid replacement does not justify waiting for dangerous potassium to correct by itself.
Waterhouse-Friderichsen syndrome describes adrenal hemorrhage associated with fulminant infection, classically meningococcemia. Purpura, shock, and disseminated intravascular coagulation demand immediate antimicrobial treatment and sepsis support as well as adrenal coverage when indicated. Bilateral adrenal hemorrhage also occurs with other infections, coagulopathy, anticoagulation, and severe physiological stress. It should not be explained as a simple mechanical failure of one vein or treated as proof of one pathogen. [6][7]
After stabilization, clarify the cause, document an individualized replacement and illness plan, and check that the patient can obtain and administer emergency medicine. Understanding the plan is necessary, but access to medicine and a workable response to vomiting are what make it usable.
Try it here · Checkpoint 3 of 3
Make your prediction before reading the choices. A first attempt is just a starting point.
Case 26
Show answer and explanations for case 26
A. Wait for a pathogen name before giving antimicrobials. (Why this does not fit)
Suspected severe bacterial sepsis requires urgent treatment before definitive microbiology.
B. Treat as isolated hemorrhagic shock without antimicrobial therapy, sepsis management, or adrenal assessment. (Why this does not fit)
The fever, purpura, coagulopathy, and bilateral adrenal injury support fulminant infection with possible cortisol failure, requiring parallel treatment.
C. Assume all bilateral adrenal hemorrhage is caused by meningococcus. (Why this does not fit)
Meningococcemia is classic, but other infections and noninfectious coagulopathies can cause hemorrhage.
D. Immediate sepsis treatment, resuscitation, and adrenal crisis coverage with hydrocortisone. (Best answer)
Fulminant infection can cause hemorrhage and cortisol failure; treating one component alone is insufficient.
Takeaway: Waterhouse-Friderichsen is a clinical association requiring simultaneous infectious, circulatory, and endocrine treatment.
These original educational cases connect physiology, test interpretation, and treatment decisions. Each asks for one best answer.
Case 1
Show answer and explanations for case 1
A. Adrenal cortex. (Best answer)
Low cortisol with markedly elevated ACTH localizes failure to the adrenal gland; salt loss and hyperkalemia suggest accompanying aldosterone deficiency.
B. Anterior pituitary ACTH production. (Why this does not fit)
ACTH deficiency would be low or inappropriately normal, not markedly elevated.
C. Hypothalamic CRH production. (Why this does not fit)
Reduced CRH would usually reduce ACTH rather than produce this compensatory elevation.
D. Excess adrenal cortisol production. (Why this does not fit)
Cortisol excess contradicts the measured deficiency and usually suppresses ACTH when adrenal in origin.
Takeaway: Pair cortisol with ACTH before using symptoms to localize disease.
A. Cortisol deficiency directly causes excessive aldosterone secretion. (Why this does not fit)
Aldosterone excess does not explain the impaired free-water excretion responsible for this central-deficiency pattern.
B. Loss of vasopressin action causes renal water loss. (Why this does not fit)
Loss of vasopressin promotes dilute urine and tends to raise sodium when water intake cannot compensate; cortisol deficiency instead promotes water retention.
C. Reduced aldosterone secretion produces primary renal salt loss. (Why this does not fit)
This mechanism is important in primary adrenal disease. Aldosterone is usually preserved in an isolated central cortisol deficit.
D. Cortisol deficiency impairs free-water excretion through increased vasopressin activity. (Best answer)
Water retention can lower sodium despite preserved aldosterone.
Takeaway: Hyponatremia is not restricted to primary adrenal disease.
A. Start thyroid replacement alone. (Why this does not fit)
Thyroid hormone does not treat acute cortisol deficiency and can worsen an uncovered deficit.
B. Complete outpatient pituitary testing before starting replacement. (Why this does not fit)
Visual impairment and hypotension make this an emergency; diagnostic scheduling must not delay glucocorticoid treatment.
C. Urgent assessment for pituitary apoplexy with glucocorticoid coverage and specialist emergency care. (Best answer)
Acute mass-related neurological signs and circulatory compromise create an emergency with possible ACTH loss.
D. Treat the headache with analgesia and observe for spontaneous visual and hemodynamic recovery before endocrine intervention. (Why this does not fit)
Analgesia may be needed, but sudden ocular deficits with a pituitary mass require urgent endocrine and neurosurgical assessment.
Takeaway: Acute pituitary neurological symptoms can be an adrenal emergency.
A. Glucocorticoid withdrawal syndrome with adequate cortisol reserve. (Why this does not fit)
Withdrawal symptoms can overlap, but vomiting and hypotension after abrupt cessation require assessment and treatment for possible adrenal crisis rather than assuming preserved reserve.
B. New autoimmune destruction of the zona glomerulosa alone. (Why this does not fit)
Isolated mineralocorticoid loss does not fit the clear glucocorticoid-withdrawal exposure and would not explain deficient endogenous cortisol reserve.
C. Accelerated cortisol clearance from an enzyme-inducing effect of prednisone. (Why this does not fit)
The central problem after prolonged prednisone exposure is suppressed CRH/ACTH and adrenal reserve, rather than enzyme induction by prednisone.
D. Suppression of CRH and ACTH with inadequate endogenous cortisol reserve. (Best answer)
Prolonged exogenous glucocorticoid exposure can suppress the axis; normal potassium fits preserved aldosterone.
Takeaway: Long-term steroid withdrawal can produce clinically important cortisol deficiency.
A. One early normal stimulation test excludes all postoperative ACTH deficiency and eliminates the need for later reassessment. (Why this does not fit)
The timing limits this test's ability to exclude a recent central defect.
B. Recent ACTH loss precedes loss of adrenal responsiveness early after pituitary injury; arrange coverage and reassessment. (Best answer)
The gland may still respond to administered ACTH before chronic deprivation develops.
C. Stop follow-up because potassium is normal. (Why this does not fit)
Potassium often remains normal in central disease and cannot settle this question.
D. The discordance localizes the defect to the zona glomerulosa. (Why this does not fit)
The test evaluates cortisol reserve and does not localize mineralocorticoid disease. Recent ACTH loss can precede adrenal atrophy.
Takeaway: Testing performance depends on how long the suspected defect has existed.
A. Recheck potassium after glucocorticoid therapy has had time to work before adding cardiac stabilization or potassium-lowering treatment. (Why this does not fit)
Severe hyperkalemia with QRS widening needs immediate cardiac stabilization and potassium-lowering measures; waiting risks arrhythmia.
B. Use a potassium binder alone while awaiting the steroid response (Why this does not fit)
A binder alone does not provide sufficiently rapid myocardial stabilization and potassium shifting for ECG-toxic hyperkalemia.
C. Immediate standard hyperkalemia stabilization and potassium-shifting treatment under monitoring. (Best answer)
ECG toxicity requires urgent treatment rather than waiting for steroids to restore excretion.
D. Give IV calcium alone and defer potassium-lowering treatment. (Why this does not fit)
Calcium stabilizes the myocardium but does not lower potassium; shifting and elimination measures with repeated monitoring are also needed.
Takeaway: Adrenal replacement does not replace emergency treatment of severe hyperkalemia.
