Several studies have also reported that nutritional iron deficiency alters dopaminergic neurotransmission, increasing the concentration of extracellular dopamine and reducing the activity of dopamine transporter (DAT) and D2 receptor in striatum (Youdim et al., 1989; Beard et al., 1994; Bianco et al., 2008; Unger et al., 2014). The gene discussed is SLC6A3; the disease is nutritional disorder.