The 5‐HT1A, 5‐HT2C, and 5‐HT1B serotonin receptors are localized on orexin neurons, and blunted serotonin transmission in lateral hypothalamus and perifornical area is associated with obesity, altered feeding, and sleep/wake cycles underscoring the complex role of hypothalamic serotonin in energy balance (Romanova et al., 2018). Here, HTR1B is linked to obesity due to melanocortin 4 receptor deficiency.