Objective: Primary aldosteronism (PA) is the most common form of secondar y and curable hypertension. Different germline and somatic mutations are found in aldosterone-produci ng adenoma (APA) and familial forms of the disease, while the causes of bilateral adrenal hyperplasia (BAH) remain largely unknown. Adrenalectomy is the recommended treatment for patients with APA; however, 6% of patients are no t cured and show persistent PA after surgery suggesting BAH. The objective of this study was to analyze clin ical data of patients with APA without biochemical success after adrenalectomy as well as the histological and gen etic characteristics of their adrenal glands. Design and methods: Clinical data of 12 patients with partial and absent biochemic al cure were compared to those from 39 PA patients with hormonal cure after surgery. Histologi cal, morphological, and genetic characterization of the adrenals was carried out by CYP11B2 and CYP11B1 immunostaining and by CYP11B2-guided NGS. Results: Patients with absent hormonal cure displayed a longer duration of arterial hypertension and lower lateralization index of aldosterone production. In ten patients, APAs expressing CYP11B2 were identified. No difference in histological and morphological characteristics was observed between patients with or without a hormonal cure. Somatic mutations in APA driver genes were identified in all CYP 11B2 positive APAs; CACNA1D mutations were the most frequent genetic abnormality. Conclusions: Patients with partial and absent biochemical cure were diagnos ed later and exhibited a lower lateralization index of aldosterone production, suggesting asymmetric aldosterone production in the context of BAH. Somatic mutations in adrenal glands from those patients indicat e common mechanisms underlying BAH and APA. [ABSTRACT FROM AUTHOR]