Endocrine Abstracts

Primary hyperaldosteronism secondary to bilateral adrenal hyperplasia (BAH) bears striking similarities pathophysiologically to essential hypertension. During stimulation studies to elucidate possible aberrant aldosterone responses in BAH we measured the aldosterone response to 250mcg iv synacthen after 30 and 60 minutes in 7 patients with BAH and in 20 healthy controls. Patients had diuretics withheld for at least 4 weeks and betablockers and calcium channel blockers withheld for at least 2 weeks.

Subjects were in the supine position for at least 30 minutes. For controls the serum aldosterone level (mean ±standard error) was 189 pmol/l±21 at baseline, 581 pmol/l±48 at 30 minutes and 565 pmol/l±47 at 60 minutes. In the patient group, the serum aldosterone levels were 722 pmol/l±266 at baseline, 2777 pmol/l±633 at 30 minutes and 2921 pmol/l±790 at 60 minutes. Using a cutoff aldosterone value of 1200 pmol/l at 30 minutes the synacthen test has a sensitivity of 85.7% and specificity of 100% for the diagnosis of BAH. At 60 minutes, using a cutoff value of 750 pmol/l, the sensitivity was100% and specificity was 95%.

These unexpected results are promising for the possible use of the synacthen test in the screening for hyperaldosteronism if similar findings are confirmed in adenoma patients and if further studies in patients with essential hypertension show similar clear distinction from patients with hyperaldosteronism as have been seen with controls.