PWS is believed to be a hypothalamic disease, and studies of postmortem brain tissue from adults with PWS have shown a 42% decrease in number and a 54% decrease in volume of oxytocin-expressing neurons in the paraventricular nucleus (PVN) of the hypothalamus suggested to be the cause for the insatiable hunger and decreased satiety in PWS [2,3]. The gene discussed is OXT; the disease is Prader-Willi syndrome.