Urinary 5-Hydroxyindolacetic Acid Measurements in Patients with Neuroendocrine Tumor-Related Carcinoid Syndrome: State of the Art

Carcinoid syndrome (CS), mostly associated with small intestinal neuroendocrine tumors (SI-NETs) or lung-related NETs, is characterized by symptoms related to hormonal secretion and long-term complications, including carcinoid heart disease (CHD), which potentially life-threatening. In the early stages of disease, are non-specific, leads delayed diagnoses. The availability reliable tumor markers crucial for a prompt diagnosis proper management. This review summarizes available evidence on role 24 h urinary 5-hydroxyindolacetic acid (24u5HIAA), breakdown metabolite serotonin, in diagnosis/follow-up NET-related CS, focus its potential prognostic role, while eventually attempting suggest timeline measurement during follow-up NET patients. use 24u5HIAA an established biomarker NETs CS since it shows sensibility specificity 100% 85–90%, respectively. downside 24u5-HIAA represented need urine collection risk confounding factors (foods medication), might lead false positive/negative results. Moreover, useful shorter double time correlates higher progression/disease-specific mortality. Furthermore, elevation correlated dismal prognosis because increased likelihood CHD development progression/mortality. Other interesting biochemical have been proposed, plasmatic 5HIAA, although further standardization prospective studies required define their management NETs. Meanwhile, remains most accurate biomarker.