Conn's Syndrome

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Tests
The goal when looking for Conn’s syndrome is to understand where the aldosterone is coming from and then to find out what is driving the increase. that the conclusions made from these test may then help decide whether surgery is likely to be beneficial.

Laboratory Tests
Doctors will frequently request blood renin tests along with blood and/or 24-hour urine aldosterone tests to help diagnose primary hyperaldosteronism and to monitor the effectiveness of treatment. The ratio of aldosterone to renin is used as an early test for primary hyperaldosteronism. If renin levels are low and aldosterone high, then the ratio will be significantly increased and primary hyperaldosteronism is likely to be present.

Electrolytes, usually blood sodium, potassium and sometime chloride and bicarbonate may be measured to look for an electrolyte imbalance. If they are present, then the doctor may give the patient spironolactone, a drug that blocks the action of aldosterone, to see if balance is restored.

These tests may be followed by computed tomography (CT) a scan of the adrenal glands to look for a tumour. This process can be complicated as benign adrenal tumours are relatively common, especially as people become older. Many of these benign tumours do not produce aldosterone and are found during investigations for other reasons. Determining large adrenal glands (hyperplasia) can also be tricky because the size of normal adrenal glands varies a lot from one person to the next.

If hyperplasia or an aldosterone-producing tumour is suspected, but not seen using normal procedures, then a doctor may request adrenal venous sampling. In this procedure, blood is collected from the vein that carries blood away from each adrenal gland. These blood samples are tested for aldosterone (sometimes cortisol is also measured and an aldosterone/ cortisol ratio calculated) and then the results from the two adrenal glands compared. If they are significantly different, then it is likely that an adenoma is present in the gland with the highest aldosterone concentration.

Non-Laboratory Tests

  •   Blood pressure measurement - often the first indicator of possible primary hyperaldosteronism
  •   CT (computed tomography) scan or MRI (magnetic resonance imaging) – used to locate adrenal tumours

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