Longitudinal monitoring of insulin and glucagon secretion in Caucasian women with impaired glucose tolerance (IGT) versus normal glucose tolerance (NGT), over a 12-year period, showed that β- and α-cell dysfunction are evident several years before diagnosis of IGT, and islet dysfunction is manifested by impaired glucose sensitivity of the β- and α-cells and reduced maximal insulin secretion[40]. The gene discussed is INS; the disease is Impaired glucose tolerance.