Change of Computed Tomography-Based Body Composition after Adrenalectomy in Patients with Pheochromocytoma

SIMPLE SUMMARY: Pheochromocytoma is regarded as a good human model for investigating the impact of sympathetic hyperactivity on various pathologic conditions. To determine the influence of catecholamine excess on human body composition, we compared computed tomography (CT)-based fat and skeletal muscle indices over time in a large patient population with histologically confirmed pheochromocytoma who underwent surgery. We observed considerable elevation in CT-measured visceral fat area and subcutaneous fat area, and the prevalence of visceral obesity after adrenalectomy in patients with pheochromocytoma. In contrast, there were no changes in skeletal muscle area, skeletal muscle index, and prevalence of sarcopenia. Furthermore, we observed that the severity of catecholamine excess was associated with a higher increase, especially in the subcutaneous fat area after surgery. These data provide important clinical evidence that sympathetic hyperactivity contributes to lipolysis in visceral and subcutaneous adipose tissues, whereas its impact on human skeletal muscle remains undetermined. ABSTRACT: Despite the potential biological importance of the sympathetic nervous system on fat and skeletal muscle metabolism in animal and in vitro studies, its relevance in humans remains undetermined. To clarify the influence of catecholamine excess on human body composition, we performed a retrospective longitudinal cohort study including 313 consecutive patients with histologically confirmed pheochromocytoma who underwent repeat abdominal computed tomography (CT) scans before and after adrenalectomy. Changes in CT-determined visceral fat area (VFA), subcutaneous fat area (SFA), skeletal muscle area (SMA), and skeletal muscle index (SMI) were measured at the level of the third lumbar vertebra. The mean age of all patients was 50.6 ± 13.6 years, and 171/313 (54.6%) were women. The median follow-up duration for repeat CTs was 25.0 months. VFA and SFA were 14.5% and 15.8% higher, respectively (both p < 0.001), after adrenalectomy, whereas SMA and SMI remained unchanged. Similarly, patients with visceral obesity significantly increased from 103 (32.9%) at baseline to 138 (44.1%) following surgery (p < 0.001); however, the prevalence of sarcopenia was unchanged. This study provides important clinical evidence that sympathetic hyperactivity can contribute to lipolysis in visceral and subcutaneous adipose tissues, but its impact on human skeletal muscle is unclear.