Primary Hyperaldosteronism

Question 1

Define

Answer 1

Characterized by autonomous aldosterone overproduction from the adrenal gland with subsequent suppression of plasma renin activity

Excess production of aldosterone, independent of RAS
Causing ↑sodium and water retention, leading to HTN
NaCl retention leads to ↑renal K+ loss, hypokalaemia and ↓renin release

Question 2

Causes

Answer 2

2/3 are due to a solitary aldosterone-producing adrenal adenoma (Conn’s syndrome)

1/3 are due to bilateral adrenocortical hyperplasia

• Adrenal adenoma (Conn’s syndrome) - responsible for 70% of cases
• Adrenal cortex hyperplasia (30% of cases)

RARE:

Glucocorticoid-suppressible hyperaldosteronism

Aldosterone producing adrenal carcinoma

Pathophysiology:

• Excess aldosterone leads to increased Na+ and water retention
• This leads to hypertension
• It also causes increased renal K+ loss leading to hypokalaemia
• Renin is suppressed due to NaCl retention

Question 3

Epidemiology

Answer 3

Conn’s occurs more commonly in women and in younger patients

↘ Bilateral adrenal hyperplasia occurs more commonly in men and usually presents at an older age

Question 4

Symptoms

Answer 4

May be asymptomatic:

±Signs of hypokalaemia: muscle weakness, cramps, paraesthesia, tetany

Polyuria, polydipsia (due to nephrogenic diabetes insipidus 2ndary to hypokalaemia)

Question 5

Signs

Answer 5

Hypertension

Complications of hypertension (e.g. hypertensive retinopathy)

Question 6

Investigation

Answer 6

Screening Tests

• Low Serum K+
  
  • NOTE: Serum Na+ is usually normal because the Na+ reabsorption is matched by water reabsorption
• High Urine K+
• High Plasma Aldosterone Concentration
• High aldosterone: renin activity ratio

Confirmatory Tests

• Salt Loading
  
  • Failure of aldosterone suppression following salt load confirms primary hyperaldosteronism
• Postural Test
  
  • Measure plasma aldosterone, renin activity and cortisol when the patient is lying down at 8 am
  • Measure again after 4 hrs of the patient being upright
  • Aldosterone-producing adenoma - aldosterone secretion decreases between 8 am and noon
  • Bilateral adrenal hyperplasia - adrenals respond to standing posture and increase renin production leading to increased aldosterone secretion
• CT/MRI
• Bilateral adrenal vein catheterisation
  
  • Measures adrenal vein aldosterone levels and allows you to distinguish between Conn’s syndrome and bilateral adrenal hyperplasia
• Radio-labelled cholesterol scanning
  
  • Unilateral uptake in adrenal adenomas
  • Bilateral uptake in bilateral adrenal hyperplasia

Question 7

Management

Answer 7

Bilateral Adrenal Hyperplasia

• Spironolactone
• Eplerenone can be used if the spironolactone side-effects are intolerable
• Amiloride (potassium-sparing diuretic)
• Monitor serum K+, creatinine and BP
• ACE inhibitors and CCBs may also be added

Aldosterone Producing Adenomas

• Adrenalectomy

Adrenal Carcinoma

• Surgery
• Post-operative mitotane (antineoplastic)

Question 8

Complication

Answer 8

Complications of hypertension

Question 9

Prognosis

Answer 9

Surgery may cure hypertension

Or it may make the hypertension easier to treat with anti-hypertensive medication