Pathogenesis of the disease
Conn's syndrome is based on uncontrolled, regulatory-independent (RAAS-independent) hypersecretion of aldosterone. Normally, this hormone enhances the reabsorption of sodium, chloride, and bicarbonate ions in the distal renal tubules while simultaneously increasing potassium excretion.
In adrenal adenoma or hypertrophy of the zona glomerulosa, this process is significantly amplified. Sodium retention entails water retention, causing hypervolemia (increased circulating blood volume) and tissue edema. In response to increased blood volume and blood pressure, renin production by the juxtaglomerular apparatus of the kidneys sharply decreases via negative feedback.
Clinical presentation
The clinical manifestations of Conn's syndrome comprise three main groups of symptoms — the so-called classic triad:
- Arterial hypertension. The leading syndrome; blood pressure rises from mild to moderate levels due to sodium and water retention.
- Neuromuscular disorders. Occur against the background of pronounced hypokalemia. Patients complain of muscle weakness attacks, paresthesias (numbness or tingling sensation), and in severe cases, paralysis.
- Renal symptoms. Have a characteristic staging. Initially, daily urine output may decrease. Later, compensatory polyuria develops (increased urine volume), accompanied by severe thirst (polydipsia) and nocturnal predominance of urination (nicturia). An important feature: resistance to antidiuretic drugs develops.
Laboratory markers
To confirm primary hyperaldosteronism, clinicians rely on specific changes in blood and urine tests:
- Electrolyte imbalance: hypernatremia (excess sodium) and hypokalemia (potassium deficiency).
- Acid-base status: shift of blood pH toward alkalinity, development of metabolic alkalosis.
- Hormonal profile: high aldosterone level with an abnormally low renin level.
To memorize the clinical triad of Conn's syndrome, you can use the rule "A-N-P": Arterial hypertension, Neuromuscular disorders, Renal symptoms.
Class and exam questions
How to differentiate Conn's syndrome from secondary hyperaldosteronism?
The main criterion is the renin level. In primary hyperaldosteronism (Conn's syndrome), renin is decreased due to negative feedback. In secondary hyperaldosteronism (due to heart failure or renal ischemia), renin is, conversely, significantly increased.
Why does muscle weakness occur in Conn's syndrome?
The reason lies in hypokalemia. Excess aldosterone causes the kidneys to excessively excrete potassium in the urine, which impairs normal neuromuscular conduction and can lead to paralysis.
What happens to diuresis in such patients?
Initially, urination decreases, but then compensatory polyuria develops with severe thirst and predominance of nocturnal diuresis (nicturia), while the kidneys cease to respond to antidiuretic hormones.
What else to study on this topic
- Normal functions and mechanisms of action of aldosterone
- Secondary hyperaldosteronism: etiology and pathogenesis
- Atrial natriuretic peptide (ANP) as a RAAS antagonist
- Differential diagnosis of secondary arterial hypertensions (pheochromocytoma, aortic coarctation)
- Hypoaldosteronism: causes, symptoms, and electrolyte disturbances
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