Aldosterone, CAH & phaeochromocytoma flashcards
24 high-yield MRCP Part 1 cards from the Intellect Medicos Endocrinology & Diabetes course. Try to answer each question before you open it — then study them properly with spaced repetition, which brings each card back just before you would forget it.
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Which adrenal zone secretes aldosterone, and what mainly controls its secretion?
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Zona glomerulosa; controlled mainly by the renin–angiotensin system and potassium, not ACTH.
Why? The fasciculata (cortisol) and reticularis (androgens) are ACTH-driven.
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What is the most common cause of primary hyperaldosteronism?
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Bilateral idiopathic adrenal hyperplasia.
Why? An aldosterone-producing adrenal adenoma (Conn's syndrome) is the other common cause.
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What is the first-line screening test for primary hyperaldosteronism?
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Plasma aldosterone:renin ratio (ARR).
Why? Autonomous aldosterone causes volume expansion, which suppresses renin, so the ratio is high.
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Which antihypertensive can usually be continued during aldosterone:renin ratio testing?
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Doxazosin (an alpha-blocker).
Why? Alpha-blockers have the least effect on the renin–angiotensin system, so they do not distort the ratio.
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What is the gold-standard test to distinguish a unilateral aldosterone-producing adenoma from bilateral hyperplasia?
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Adrenal vein sampling.
Why? CT/MRI is done first, but small non-functioning incidentalomas are common, so lateralisation needs adrenal vein sampling.
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What is the treatment of primary hyperaldosteronism due to bilateral adrenal hyperplasia?
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Spironolactone (a mineralocorticoid receptor antagonist).
Why? Hyperplasia is bilateral, so surgery is not curative. A unilateral adenoma is removed laparoscopically.
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A man on spironolactone develops painful gynaecomastia. Which drug can replace it?
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Eplerenone.
Why? Eplerenone is a more selective mineralocorticoid receptor antagonist with less anti-androgen effect.
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In renal artery stenosis, what are the plasma renin and aldosterone levels?
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Both high (secondary hyperaldosteronism).
Why? Reduced renal perfusion drives renin release, which drives aldosterone.
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What is the commonest cause of renal artery stenosis in a young woman?
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Fibromuscular dysplasia.
Why? Atherosclerosis is the most common cause overall, in older patients.
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In bilateral renal artery stenosis, which drug classes can cause a sharp rise in creatinine?
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ACE inhibitors and angiotensin receptor blockers.
Why? Glomerular filtration depends on angiotensin II constricting the efferent arteriole; blocking it drops GFR.
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Which gene product is overactive in Liddle syndrome, and which drug treats it?
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The epithelial sodium channel (ENaC) in the collecting duct; treat with amiloride.
Why? Excess sodium reabsorption causes hypertension and hypokalaemia with suppressed renin AND aldosterone.
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Which enzyme does liquorice inhibit to cause hypertension and hypokalaemia?
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11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2).
Why? 11β-HSD2 normally inactivates cortisol to cortisone in the kidney; without it, cortisol activates mineralocorticoid receptors. Renin and aldosterone are low.
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A normotensive patient has hypokalaemia, high renin and high aldosterone, with low magnesium and low urinary calcium. What is the diagnosis?
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Gitelman syndrome.
Why? Gitelman is a thiazide-like defect of the distal tubule Na–Cl co-transporter. Bartter syndrome (loop-like defect) has normal or high urinary calcium.
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What is the most common enzyme deficiency in congenital adrenal hyperplasia?
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21-hydroxylase deficiency (about 90%).
Why? Cortisol and aldosterone are low, so ACTH rises and precursors are shunted into androgens.
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Which blood test is used to diagnose classical 21-hydroxylase deficiency?
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Raised 17-hydroxyprogesterone (17-OHP).
Why? 17-OHP is the substrate that builds up behind the 21-hydroxylase block.
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A 10-day-old boy with normal genitalia presents with vomiting, dehydration and collapse. Sodium is 124 mmol/L and potassium 7.1 mmol/L. What is the most likely underlying diagnosis?
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Salt-wasting congenital adrenal hyperplasia (21-hydroxylase deficiency).
Why? Boys have no ambiguous genitalia to prompt early diagnosis, so they present with a salt-losing crisis in the first weeks of life.
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Which form of congenital adrenal hyperplasia causes virilisation together with HYPERtension and hypokalaemia?
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11β-hydroxylase deficiency.
Why? 11-deoxycorticosterone builds up; it is a weak mineralocorticoid that causes salt retention. Androgens are also raised.
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Non-classical CAH in a young woman is easily mistaken for which condition?
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Polycystic ovary syndrome (hirsutism, oligo/amenorrhoea).
Why? Milder enzyme deficiency presents only in adolescence or adulthood. A raised early-morning 17-OHP, confirmed by a high 17-OHP after Synacthen (ACTH) stimulation (course notes: >33 nmol/L), makes the diagnosis.
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What is the first-line biochemical test for suspected phaeochromocytoma?
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Metanephrines — plasma free metanephrines or 24-hour urinary fractionated metanephrines.
Why? Metanephrines are made continuously inside the tumour, so they are more sensitive than catecholamines, which are released in bursts.
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Which nuclear medicine scan localises a phaeochromocytoma by specific uptake into catecholamine-producing tissue?
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MIBG (meta-iodobenzylguanidine) scan.
Why? Cross-sectional imaging (MRI/CT abdomen) is used first; MIBG helps with extra-adrenal or metastatic disease.
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What is the first drug given to prepare a patient with phaeochromocytoma for surgery?
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An alpha-blocker — phenoxybenzamine.
Why? A beta-blocker is added only after adequate alpha-blockade; beta-blockade first leaves alpha-stimulation unopposed and can cause a hypertensive crisis.
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What type of alpha-blocker is phenoxybenzamine?
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An irreversible (non-competitive), non-selective alpha-blocker.
Why? Irreversible blockade cannot be overcome by surges of catecholamine from the tumour.
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Name three genetic syndromes associated with phaeochromocytoma.
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MEN 2A, MEN 2B, neurofibromatosis type 1 and von Hippel–Lindau syndrome (any three).
Why? Hereditary cases are more often bilateral and are screened with plasma free metanephrines.
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What is the rate-limiting enzyme in catecholamine synthesis?
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Tyrosine hydroxylase (tyrosine → DOPA).
Why? DOPA → dopamine → noradrenaline → adrenaline. Noradrenaline and adrenaline are broken down to normetanephrine and metanephrine, then VMA.
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