Reduced Sympathetic Metabolites in Urine of Obese Patients With Craniopharyngioma

Abstract

Severe obesity is a major problem in patients suffering from craniopharyngioma (CP), a benign tumor located in pituitary and hypothalamic regions. In this study, the hypothesis that hypothalamic damage leads to a reduction in overall sympathetic tone was tested. Catecholamines, as well as their metabolites homovanillic acid (HVA) and vanillylmandelic acid (VMA), markers of catecholamine turnover, were measured in morning voided urine of 109 patients participating in a German pediatric CP study, and their physical activity was analyzed using a questionnaire. HVA and VMA results were compared with age-matched HVA and VMA in urine of patients proven to not have a catecholamine-secreting tumor. Patients with the most severe obesity displayed the lowest urine HVA and VMA values. Patients with hypothalamic CP had 3.2-fold higher BMI values (p<0.0001), lower HVA (0.72-fold, p<0.001), and VMA (0.84-fold, p<0.01) values, and significantly lower activity scores than those without hypothalamic involvement, but their epinephrine- and norepinephrine/creatinine ratios were not significantly different, possibly due to low levels. The low HVA and VMA values suggest decreased sympathetic outflow contributing to reduced physical activity and severe obesity, especially in patients with a hypothalamic tumor. In further studies investigating treatment options for hypothalamic obesity, disturbed sympathetic tone should be considered.