['Altered brain dopaminergic and serotonergic pathways have been shown in obese rodents and humans, but it is unknown whether this is related to obesity per se or to the metabolic derangements associated with obesity.', 'We performed a case-control study in insulin sensitive obese (ISO) and insulin resistant obese (IRO) subjects (n = 12) and age-matched lean controls (n = 8) and measured serotonin transporter (SERT) binding in the whole diencephalon and specifically in the hypothalamus, as well as dopamine transporter (DAT) binding in the striatum using 123I-FP-CIT single photon emission computed tomography (SPECT). We assessed insulin sensitivity using the HOMA-IR.', 'BMI did not differ between the IRO and ISO subjects. SERT binding in the diencephalon was significantly lower in IRO vs ISO subjects but was not different between lean and obese subjects. SERT binding in the hypothalamus tended to be reduced in obese vs lean subjects, but was not different between IRO and ISO subjects. Striatal DAT binding was similar between lean and obese subjects as well as between ISO and IRO subjects.'] Is serotonin Transporter Binding in the Diencephalon Reduced in Insulin Resistant Obese Humans?