Conn Syndrome (Primary Hyperaldosteronism)
Background Information
Definition
Conn syndrome (primary hyperaldosteronism) is defined by the autonomous overproduction fo aldosterone in 1 or both adrenal glands
Aetiology
There are 2 main causes: [Ref]
- Bilateral adrenal hyperplasia (idiopathic) – most common
- Aldosterone-producing adenoma – 2nd most common
Clinical Features
Main clinical features: [Ref]
- Drug-resistant hypertension
- Conn syndrome is the most common endocrine cause of secondary hypertension
- Features of hypokalaemia
- Fatigue
- Muscle cramping / weakness
- Paraesthesia
- Polyuria and polydipsia
- Constipation
Diagnosis
Non-Diagnostic Tests
Key biochemical changes: [Ref]
- Hypernatraemia
- Hypokalaemia
- Metabolic alkalosis
Actions of aldosterone:
- ↑ Sodium and water retention
- ↑ Potassium excretion
- ↑ Acid excretion
By learning the actions of aldosterone, you would have learned the biochemical changes in both Conn syndrome (primary hyperaldosteronism) and adrenal insufficiency.
Endocrine Tests
1. Confirming Conn Syndrome
1st line: measure serum aldosterone and renin activity [Ref]
- ↑ Aldosterone + ↓ renin is suggestive of Conn syndrome
- NB if both renin and aldosterone are raised, that is likely secondary hyperaldosteronism
Confirmatory test (not routinely performed): saline suppression test [Ref]
- If saline load failed to suppress aldosterone levels → Conn syndrome is very likely
2. Identifying Underlying Cause
The 2 main causes to differentiate between are 1) unilateral aldosterone-producing adrenal adenoma and 2) bilateral adrenal hyperplasia.
Choice of test: [Ref]
- 1st line: CT adrenals
- Gold standard: adrenal venous sampling (definitively differentiates between unilateral and bilateral aldosterone overproduction)
Management
Management
Management depends on the underlying cause: [Ref]
| Underlying cause | Management |
|---|---|
| Aldosterone-producing adrenal adenoma |
|
| Bilateral adrenal hyperplasia |
|
Therefore, it makes sense to only offer surgery in a unilateral cause (i.e. aldosterone-producing adrenal adenoma), but avoid surgery in a bilateral cause (i.e. adrenal hyperplasia).