For example, in a previous study, to evaluate the association between circulating leptin concentration and the severity of GBM and cholelithiasis, patients in the GBM and cholelithiasis groups were separated into those that underwent surgery owing to clinical manifestations and those that did not; serum leptin concentrations were found to be significantly higher in the operated group than in the nonoperated group. The gene discussed is LEP; the disease is glioblastoma.