A 53-year-old man returns for a review of his antihypertensive medication. He has attended multiple times, and his blood pressure has remained persistently elevated despite optimal therapy.
He reports increasing fatigue and wonders if his symptoms are due to his current medication.
Medications:
- Ramipril 10 mg OD
- Amlodipine 10 mg OD
- Bendroflumethiazide 2.5 mg OD
He takes no other drugs and has no known allergies.
24-hour BP monitoring: Average BP 161/92 mmHg
Recent blood tests:
- Hb: 14.6 g/dL
- WCC: 5.6 × 10⁹/L (Neutrophils: 2.8)
- Sodium: 147 mmol/L
- Potassium: 2.9 mmol/L
- Urea: 5.8 mmol/L, Creatinine: 87 µmol/L
- TSH: 3.4 mU/L
- Free T4: 5.3 pmol/L
- Random glucose: 8.1 mmol/L
Show Answer
The most likely diagnosis is primary hyperaldosteronism, also known as Conn’s syndrome, when caused by an adrenal adenoma. In this case, the presence of difficult-to-control hypertension, persistent hypokalaemia, and a high-normal sodium level strongly points towards an underlying mineralocorticoid excess.
Primary hyperaldosteronism is now recognised to be far more common than previously thought and may account for up to 10–15% of cases previously labelled as essential hypertension. The prevalence is even higher among patients with resistant hypertension, spontaneous or diuretic-induced hypokalaemia, and older individuals.
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Initial screening involves measuring the plasma aldosterone-to-renin ratio (ARR). A high ratio (typically >30) in the presence of an elevated aldosterone level is highly suggestive of primary hyperaldosteronism.
Once the diagnosis is suspected or confirmed biochemically, imaging is required to identify the underlying cause. A high-resolution CT scan of the adrenal glands is usually the first-line imaging modality to look for an adrenal adenoma or evidence of bilateral adrenal hyperplasia.
However, imaging alone is often not sufficient. Many incidental non-functioning adrenal adenomas are found in the general population, especially in older adults, which can lead to misdiagnosis. Therefore, adrenal venous sampling (AVS) is recommended in most cases before surgery to confirm that aldosterone hypersecretion is unilateral. AVS helps distinguish between a surgically correctable adenoma and bilateral disease, which would be managed medically.
Show Answer
If the patient is found to have an adrenal adenoma and lateralisation is confirmed with adrenal venous sampling, the preferred treatment is surgical removal of the affected adrenal gland. Prior to surgery, a short trial of spironolactone is often initiated to correct hypokalaemia and assess clinical response.
In contrast, if the diagnosis is bilateral adrenal hyperplasia, surgical intervention is not appropriate. These patients are best managed with long-term mineralocorticoid receptor antagonists, such as spironolactone or eplerenone. Eplerenone may be better tolerated, particularly in male patients, as it is associated with fewer anti-androgenic side effects.
