Primary Hyperaldosteronism (Conn Syndrome)
Endocrinology
Illness script · Endocrinology
Primary Hyperaldosteronism (Conn Syndrome)
Autonomous adrenal aldosterone overproduction causing resistant hypertension, hypokalemia, and metabolic alkalosis with suppressed renin.
This illness script for Primary Hyperaldosteronism (Conn Syndrome) covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Most common cause of secondary hypertension (~5–10% of hypertensives)
- Ages 30–50; slight female predominance
- Aldosterone-producing adenoma (~35%) or bilateral adrenal hyperplasia (~60%)
- Suspect in: resistant HTN on ≥3 drugs, spontaneous hypokalemia, or adrenal incidentaloma
- Rare: familial hyperaldosteronism (glucocorticoid-remediable aldosteronism)
02
Presentation
- Resistant hypertension (often on 3+ antihypertensives)
- Hypokalemia: muscle weakness, cramps, palpitations (absent in up to 50%)
- Metabolic alkalosis; polyuria/nocturia from hypokalemia-induced nephrogenic DI
- No peripheral edema despite Na⁺ retention (aldosterone escape mechanism)
- Headache common; symptoms may be subtle or absent
03
Pathophysiology
- Autonomous aldosterone secretion independent of renin-angiotensin-II stimulation
- Aldosterone acts on collecting duct: Na⁺/water retention → volume expansion → hypertension
- K⁺ and H⁺ wasting → hypokalemia and metabolic alkalosis
- Volume expansion suppresses renin — the hallmark distinguishing primary from secondary
04
Diagnostics
- First-line: Aldosterone-to-renin ratio (ARR) >30 with aldosterone >15 ng/dL is suspicious
- Confirmatory: IV or oral salt loading — failure to suppress aldosterone confirms autonomy
- CT adrenal: identify adenoma vs. hyperplasia (not sufficient alone for surgical planning)
- Gold standard for lateralization: Adrenal vein sampling (AVS) before any surgery
- Key pitfall: spironolactone, ARBs, diuretics alter ARR — wash out before testing
05
Management
- Unilateral adenoma → laparoscopic adrenalectomy (curative in majority)
- Bilateral hyperplasia → spironolactone first-line; eplerenone if gynecomastia/side effects
- Correct hypokalemia pre-operatively; spironolactone bridges to surgery
- Post-adrenalectomy: monitor for hyperkalemia and transient hypoaldosteronism
- Avoid empiric diuretics — worsen hypokalemia and mask diagnosis
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Secondary hyperaldosteronism (e.g., renovascular HTN, heart failure)
Renin is HIGH in secondary hyperaldosteronism; Conn Syndrome has suppressed (low) renin.
Cushing Syndrome
Cushing's has hypercortisolism signs (moon facies, striae, buffalo hump) with normal or mildly elevated aldosterone-to-renin ratio.
Liddle Syndrome
Liddle's has the same phenotype (HTN, hypokalemia, low renin) but aldosterone is LOW — gain-of-function ENaC mutation.
Essential hypertension with diuretic use
Diuretic-induced hypokalemia has normal ARR and renin is NOT suppressed; stops with drug cessation.
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Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.