Unilateral adrenalectomy partially improved hyperglycemia in a patient with primary bilateral macronodular adrenal hyperplasia.

Primary bilateral macronodular adrenal hyperplasia (PBMAH) is characterized by bilateral multiple adrenal macro-nodules that often cause mild over-secretion of cortisol in the form of subclinical Cushing's syndrome. We herein describe a case, wherein unilateral adrenalectomy partially improved hyperglycemia in a patient with PBMAH and suggest the usefulness and limitations of this surgical strategy. A 64-year-old woman with type 2 diabetes had an incidental diagnosis of bilateral adrenal lesions. She had a family history of type 2 diabetes, and her HbA1c level was 8.9% under insulin therapy. She did not present with any symptoms associated with Cushing's syndrome. The basal cortisol level was in the normal range (12.0 μg/dL); however, the adrenocorticotropic hormone (ACTH) level was suppressed (2.1 pg/mL) and the serum cortisol level was not suppressed in the dexamethasone test. Computed tomography and magnetic resonance imaging showed bilateral adrenal macro-nodules and 131I-adosterol accumulated in the bilateral adrenal lesions. Collectively, she was diagnosed with subclinical Cushing's syndrome due to PBMAH complicated with diabetes mellitus, hypertension, and dyslipidemia. Laparoscopic left adrenalectomy was performed, and the pathologic findings were consistent with PBMAH. After unilateral adrenalectomy, serum cortisol levels decreased, and hypertension improved. Both HbA1c levels and insulin requirement also decreased, but insulin therapy was continuously needed. It should be noted that hyperglycemia may not be cured after successful surgery in a patient with PBMAH. Additional operation or medical therapy should be considered if unilateral adrenalectomy is unable to correct hypercortisolism in PBMAH patients. © The Japan Diabetes Society 2021.