Diagnosing Variable Primary Aldosteronism.

Inclusion Criteria: * People with clinically suspected PA but have not met criteria for diagnosis. Suspicion based on low-renin (renin activity \<0.5 nmol/h/L or renin mass \<5 ng/L), plasma sodium \> 140mmol/L or plasma potassium \< 4mmol/L. * Patients who have been diagnosed with PA and had previous aldosterone samples \<277 pmol/L, a level which would normally not qualify for confirmatory testing. * Patients with aldosterone results done at different times that indicate variability in production. * Willing to consent and participate in the study. Exclusion Criteria: * Inability to withdraw β-adrenoceptor antagonist therapy for 2 weeks. * People on end of life treatment.