Role of NP-59 SPECT/CT in the Management of Mild Autonomous Cortisol Secretion

Background/Objectives: Recent advancements in medical imaging have provided tools that significantly enhance diagnostic precision and patient care. Among these, NP-59 SPECT/CT imaging has emerged as a promising method for assessing adrenal gland functionality. Current gaps in clinical practice, including the lack of specific diagnostic biomarkers and the paucity of clinical trials demonstrating the efficacy of adrenalectomy in alleviating comorbidities, necessitate the search for other diagnostic methods. Management becomes more challenging when bilateral adrenal adenomas are present. Demonstrating lateralization in cortisol secretion may greatly assist in treatment selection. Unilateral secretion of cortisol indicates autonomy and therefore adrenalectomy should be preferred. The aim of this study was to evaluate the usefulness of NP-59 SPECT/CT in the management of MACS. Methods: We investigated 20 patients with benign bilateral adrenal incidentalomas and MACS between the years 2023 and 2025. The first group (70%) consisted of patients with only hypertension, without additional comorbidities (hypertension only, HO). The second group (30%) consisted of hypertensive patients with additional comorbidities (hypertension with comorbidities, HC). Visualizations of adrenal glands metabolic activity were conducted using the SPECT/CT system after intravenous injection of NP-59. Abdominal SPECT/CT was performed at 3, 5, and 7 days after tracer injection. Lateralization was established when only single adrenal uptake occurred as early as the third day. Results: Six (30%) patients demonstrated lateralization during NP-59 SPECT scintigraphy. All these patients belonged to the HO group and accounted for 43% of it. Conclusions: NP-59 SPECT scintigraphy is valuable in the identification of unilateral cortisol secretion and guiding treatment decisions such as adrenalectomy versus conservative management. Prospective studies are needed to determine its clinical utility.