A 53-year-old man returns to your GP surgery for review of his blood pressure medication. He has been seen several times and you have been finding his hypertension difficult to control. He also states that he has been feeling very tired and fatigued of late and is worried that this is the result of the blood pressure medication that he has been prescribed.

Presently he is taking rampiril 10 mg, amlodipine 10 mg and bendroflumethiazide 2.5 mg, all once daily. He is not taking any other medications and has no know drug allergies.

You recently organised for him to have 24-hour blood pressure monitoring, which showed that his BP was consistently elevated, with an average reading of 161/92, despite his current medication regime.

A recent set of blood results has been organised to investigate his tiredness and the results are shown below:

Hb: 14.6 g/dL
White cell count: 5.6 x 109/L
Neutrophils: 2.8 x 109/L
Potassium: 2.9 mmol/L
Sodium: 147 mmol/L
Urea: 5.8 mmol/L
Creatinine: 87 μmol/L
TSH: 3.4 mU/L
Free T4: 5.3 pmol/L
Random plasma glucose: 8.1 mmol/L

1. What is the most likely diagnosis in this case?

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The most likely diagnosis in this case is primary hyperaldosteronism secondary to an adrenal adenoma (Conn’s syndrome) or bilateral idiopathic adrenal hyperplasia.

The diagnosis of primary hyperaldosteronism is likely in any patient with a combination of difficult to control hypertension, hypokalaemia and an elevated or high normal sodium. Evidence now suggests that the prevalence of primary hyperaldosteronism is much higher than previously thought and it may be responsible for as many as 10-15% of cases of essential hypertension. It has a higher prevalence amongst patients with resistant hypertension, in patients with hypokalaemia and also in the elderly.

2. How can this diagnosis be confirmed?

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Patients with suspected primary hyperaldosteronism should be screened with a plasma aldosterone: renin activity ratio. A raised aldosterone: renin ratio (>30) is highly suggestive of primary hyperaldosteronism.

Once this has been confirmed it is necessary to distinguish between an adrenal adenoma and bilateral adrenal hyperplasia. High-resolution CT scanning with contrast is an excellent means of doing this and has a sensitivity of greater than 90%.

In some cases it can be difficulty to distinguish between an adenoma and adrenal hyperplasia and MRI can be used to help distinguish indeterminate CT lesions. The picture is further complicated by the fact that some CT scans detect non-functioning adenomas, which actually represent areas of hyperplasia.

3. What is the management of this condition?

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Hyperaldosteronism secondary to an adenoma is generally treated with 4 to 6 weeks of spironolactone therapy followed by surgical removal of the adenoma. It is advisable that patients with a suspected adenoma undergo adrenal venous sampling prior to surgery to confirm the diagnosis

Adrenal hyperplasia tends to respond well to potassium sparing diuretics alone, such as spironolactone or amiloride.

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