The role of biochemical tests and clinical symptoms in differential diagnosis of primary aldosteronism.

BACKGROUND

Primary aldosteronism (PA) is a secondary form of hypertension resulting from the autonomous hypersecretion of aldosterone. The recognition of PA has an important impact on clinical management, since the choice of therapy is different - surgical for adenoma and medical for hyperplasia.

AIM

To evaluate patients with PA in regard to clinical and biochemical factors differentiating between adenoma of adrenal cortex (APA) and idiopathic adrenal hyperplasia (IHA).

METHODS

We retrospectively analysed 62 patients with PA (33 females, 29 males, mean age 49.3+/-12.5 years, range 26-78) diagnosed in the Department of Hypertension between 1990-2001. In 37 patients (mean age 47.4+/-12.1 years, 22 females, 15 males) APA was diagnosed whereas in the remaining 26 patients (mean age 52.2+/-12.6 years, 14 males, 11 females) IHA was detected. Clinical manifestation, biochemical, serum aldosterone (SA), plasma renin activity (PRA) as well as echocardiographic parameters and blood pressure (BP) levels were evaluated. Diagnostic accuracy of computed tomography (CT) and scintigraphy was also assessed.

RESULTS

Mean systolic BP was significantly higher in the patients with APA. Both groups had similar mean diastolic BP. Severe hypertension, resistant to three or more medications, was found in 63.3% of all patients. Muscle weakness was reported by 39.7% of patients, polyuria - by 19%, and polydypsia - by 10.3% of patients. Patients with muscle weakness had higher mean systolic BP level and lower plasma potassium level than patients without this complaint. Symptoms suggesting cardiac arrhythmia were reported by 45% of patients. A normal potassium level was found in 25.8% of all patients. The hypokalemic patients were younger, had shorter known duration of hypertension, higher mean systolic BP level and higher SA concentration than the normokalemic patients. Supine SA levels were significantly higher in the APA group than in the IHA group (50.3+/-29.0 ng% vs 30.5+/-14.7 ng%; p<0.001). The SA/PRA ratio higher than 30:1 was found in all patients. Response to postural test with a rise in SA concentration higher than 30% was observed in 40% patients with APA and in 87.5% patients with IHA (p<0.0001). There was a strong correlation between supine and upright SA level, and systolic and diastolic BP level as well as plasma potassium level. Left ventricular hypertrophy was present in 60% of patients. The differentiation between APA and IHA was possible using CT, scintigraphy or both methods in 75%, 89.2% and 100% of patients, respectively.

CONCLUSIONS

One quarter of patients with PA were normokalemic. PA should be suspected especially in patients with severe hypertension, resistant to three or more antihypertensive drugs. Changes in SA concentration during the postural tests such as CT and scintigraphy are useful for differentiation between APA and IHA.