Endocrine and metabolic · Moderate
This case is fictional and exists for study. It describes no real patient.
38 years · female
A 38-year-old female presents to the emergency department with a 3-month history of worsening fatigue, generalized weakness, unintentional weight loss of 6 kg, and recurrent nausea. Over the past 2 days, she has developed severe dizziness upon standing and mild diffuse abdominal pain. Physical examination reveals generalized hyperpigmentation, most prominent over her palmar creases, surgical scars, and buccal mucosa. Her lying blood pressure is 92/58 mmHg, dropping to 76/44 mmHg upon standing. Initial blood investigations show hyponatraemia, hyperkalaemia, and mild hypoglycaemia.
Vital signs
- HR
- 108 bpm
- BP
- 92/58 mmHg
- RR
- 18/min
- Temp
- 36.7 °C
- SpO₂
- 98%
Examination findings
- Hyperpigmentation of palmar creases and buccal mucosa
- Postural drop in blood pressure
- Mild diffuse abdominal tenderness without peritonitis
Investigations
| Serum Sodium | 128 mmol/L | reference: 135-145 |
| Serum Potassium | 5.6 mmol/L | reference: 3.5-5.0 |
| Serum Glucose | 3.6 mmol/L | reference: 4.0-5.4 |
| Serum Urea | 9.2 mmol/L | reference: 2.5-7.8 |
Question 1 of 3
Which of the following is the most likely diagnosis?
Primary adrenal insufficiency (Addison's disease) is characterized by loss of both glucocorticoids and mineralocorticoids. Loss of cortisol leads to decreased negative feedback, increasing ACTH levels which causes characteristic skin and mucosal hyperpigmentation. Loss of aldosterone leads to renal sodium wasting and potassium retention (hyponatraemia, hyperkalaemia, hypotension). Secondary adrenal insufficiency (pituitary aetiology) presents without hyperpigmentation (low ACTH) and usually preserves mineralocorticoid secretion. Anorexia nervosa and hypothyroidism do not cause hyperpigmentation, hyperkalaemia, or primary aldosterone deficiency.
Teaching point: Hyperpigmentation combined with hyperkalaemia and hyponatraemia distinguishes primary adrenal insufficiency from secondary adrenal insufficiency.
Question 2 of 3
Which of the following is the most definitive diagnostic investigation to confirm primary adrenal insufficiency?
The Short Synacthen test (ACTH stimulation test) is the gold standard diagnostic test for adrenal insufficiency. Serum cortisol is measured before and 30 or 60 minutes after administration of synthetic ACTH (tetracosactide/cosyntropin); failure of cortisol to rise above the diagnostic threshold (<450-500 nmol/L) confirms adrenal insufficiency. 24-hour urinary free cortisol and dexamethasone suppression tests are used in diagnosing Cushing's syndrome (cortisol excess), not insufficiency. The aldosterone-to-renin ratio is used to screen for primary hyperaldosteronism (Conn's syndrome).
Teaching point: The Short Synacthen (ACTH stimulation) test is the definitive diagnostic investigation for primary adrenal insufficiency.
Question 3 of 3
Which of the following is the most appropriate immediate management step while awaiting diagnostic confirmation?
In a patient presenting with haemodynamic instability and suspected adrenal crisis, immediate resuscitation with intravenous 0.9% sodium chloride solution and IV hydrocortisone (100 mg) is critical and life-saving. Treatment should never be delayed for diagnostic testing when an acute crisis is suspected. Oral fludrocortisone is used for long-term mineralocorticoid replacement, not acute stabilization. Hyperkalaemia in adrenal crisis is driven by mineralocorticoid deficiency and corrects rapidly with fluid replacement and hydrocortisone (which has sufficient mineralocorticoid activity at high doses).
Teaching point: Suspected acute adrenal crisis requires immediate treatment with IV 0.9% saline and IV hydrocortisone without waiting for diagnostic test results.
Key learning points
- Primary adrenal insufficiency involves destruction of the adrenal cortex, causing deficiency of both cortisol and aldosterone.
- Hyperpigmentation of palmar creases and buccal mucosa is a hallmark of elevated ACTH levels seen in primary, but not secondary, adrenal insufficiency.
- Acute or impending adrenal crisis is a medical emergency requiring rapid intravenous fluid resuscitation and high-dose IV hydrocortisone.
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