What types of hyperaldosteronism are there, and what basic features characterise each?

• Primary hyperaldosteronism: or Conn's syndrome, due to autonomous secretion by the adrenal cortex

• Secondary: associated with increased levels of hormones of the renin-angiotensin-aldosterone (R-A-A) system, e.g. following dehydration, blood loss, cardiac and liver failure with third-spacing of fluid. Also occurs with renal artery stenosis

2. What causes Conn's syndrome?

It is most often due to a single (rarely more) adenoma of the zona glomerulosa of the adrenal cortex. Also following idiopathic bilateral hyperplasia of the zona glomerulosa.

3. What is the dominant clinical feature?

Hypertension due to chronic salt and water retention. Peripheral odema is not, however, usually present despite water excess – the mechanism for this is not understood fully.

4. What biochemical abnormalities might you detect?

• Hypernatraemia: following salt retention. However, water retention may lead to a normal plasma [Na+]

• Hypokalaemia: patients may have associated muscle weakness and cardiac arrhythmias

• Metabolic alkalosis: associated with hypokalaemia and loss of H+ following increased exchange with Na+ at the kidney

5. What will the urine show?

• Increased potassium

• Low sodium

• High aldosterone concentrations

6. Apart from the important features mentioned above, what other clinical feature commonly occurs with Conn's syndrome?

Ployuria. This is due to tubular nephropathy, leading to a reversible diabetes insipidus.

7. Which aldosterone antagonist has been used in the medical management of this disorder?

The diuretic spironalactone.

8. What are the most common causes of Cushing's syndrome of cortisol excess?

In their order of frequency:

• Iatrogenic steroid administration

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