CONN'S SYNDROME

DEFINITION
A condition involving oversecretion of a salt and water regulating hormone of the adrenal gland, classically leading to muscle and sensation problems and high blood pressure, caused by a hyper-functioning benign tumour.

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INCIDENCE

FM 2-5:1
Commonest in 30s-40s
In as many as 0.5-2% of unselected hypertensive patients
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AETIOLOGY
Adrenal adenoma, usually unilateral
Unclear what causes this to develop.
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BIOLOGICAL BEHAVIOUR

Pathophysiology
Tend to be small (<2 cm), slow growing, solitary, encapsulated and thoroughly benign lesions growing more commonly on the left.
Strangely, us. composed of zona fasciculata cells (zona glomerulosa secretes aldosterone normally), uniform in shape and size, mature.
Don't progress to Ca
Secrete aldosterone -> K+ loss, Na+ retention in kidney
--> also resultant retention of H+ and Mg2+ due to Na+ exchange effects.

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MANIFESTATIONS

1. Hypertension and hypokalaemia
2. Hypertension resistant to medical therapy.

Symptoms
K+ loss
Muscle weakness, tetany, paralysis (rare & extreme), paraesthaesia, headaches, visual disturbances.
Unlikely severe enough to cause arrhythmias

Na+ retention
Symptoms resultant of hypertension, e.g. headache especially on walking, blurred vision, dizziness, needing to urinate at night.
Rarely severe enough to cause fits, severe headaches, epistaxis and stroke.
Chronically it has end-organ effects.

H+ loss (rarely profound)
Slight alkalosis.
May contribute to tetany

Combined
Inability to concentrate urine -> polydipsia, polyuria

Signs
Hypertension usually diastolic and not usually severe
Check for neuro manifestations of hypokalaemia.

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INVESTIGATIONS

Investigations must differentiate hyperplasia (treated medically) from adenoma (treated surgically)

1. Electrolytes
Depressed renin (also found in 25% of essential hypertensives)
Elevated aldosterone (renin:aldosterone ratio most sensitive for diagnosis)
- plasma aldosterone concentration > 15ng/dL
- suppressed renin concentration <0.5 ng/mL/hr
- ratio is 30 or greater; else secondary hyperaldosteronism likely.

2. Imaging
If suspected primary hyperaldosteronism.
CT (spiral, thin 2mm slice protocol)
- accurate for detecting adenomas >0.5cm
--> benign: 10-15HU or lower on unenhanced CT; 10-min delayed CT washout >50%; 15-min delayed CT washout >60%.
MRI: very accurate for lipid content of adenomas; accuracy of greater than 90%.


3. Sampling
May need percutaneous transfemoral bilateral adrenal vein catheterisation with vein sampling
- may have a concurrent functioning microadenoma / hyperplasia in other side in up to 20%
--> argues for routine use of adrenal vein sampling
--> if 5x higher on one side than other, diagnostic of unilateral functioning adenoma.

Algorithm
image
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MANAGEMENT


Non-operative : for bilateral adrenal hyperplasia
Aldosterone antagonists (spironolactone - 100-400mg daily)
Other treatment for hypertensive control, especially Ca2+ channel blockers

Pre-op Work-up
Preop 3-5wk course of spironolactone 100-400mg/day and/or oral potassium
Preop normalization of blood pressure is a good sign of likely success from surgery
Spironolactone and potassium supplements should be stopped post-op.
Do not need steroid replacements for a unilateral procedure.

Operative
Adrenalectomy
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