HTR2B and heart valve disorder: For example, 5-HT2B serotonin receptors may serve as a molecular target responsible for fenfluramine-induced valvular heart disease as receptoromic screening indicated that norfenfluramine, via activating 5-HT2B serotonin receptors, was a potential agent responsible for valvular heart disease and pulmonary hypertension (Figure 2; Fen-phen [92–95]).