Aberrant and upregulated eutopic receptors have been identified in vitro in patients with primary aldosteronism (PA). We previously identified an exaggerated aldosterone response to synacthen in patients with PA versus healthy controls. In this study we aimed to evaluate whether the synacthen test differentiates between patients with PA and essential hypertension (EH). The 250 mcg intramuscular synacthen test was performed after 30 minutes recumbency in the morning and off interfering medications in ten patients with PA (7 aldosterone producing adenoma (APA), 3 bilateral adrenal hyperplasia (BAH)), 14 with EH (normal aldosterone to renin ratio) and 14 normotensives. PA was confirmed with saline suppression testing and classified using CT imaging and adrenal venous sampling. Serum aldosterone and cortisol were measured at 0, 30 and 60 minutes. Differences were compared using one way analysis of variance. Aldosterone was significantly higher in the PA group compared to the EH and normotensive groups at all three time points (P=<0.001 at 0, 30 and 60 minutes). The area under the curve (AUC) on receiver operating curve analysis was greatest at T=60 minutes (AUC: 0.96, P=<0.001). There was also maximal separation between groups at this time point. There was no difference in cortisol response between groups and no difference in response between APA and BAH patients. This study demonstrated an exaggerated aldosterone response to ACTH in patients with PA compared to those with essential hypertension and normotensive controls. This was a small study however if confirmed in larger numbers and in patients taking anti-hypertensive medications, the synacthen test may prove to be a useful diagnostic tool for PA.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.