These findings are similar to those reported in the global heterozygous- (46) or β-cell-specific (9) Prlr null mice on a C57BL/6 background, but contrast with those on a 129/SvJ background, where global deletion of the PRLR associated with glucose intolerance, reduced islet density and β-cell mass, and lower pancreatic insulin expression and release (7), and also in mice on a mixed C57BL/6-129/SvJ background with deletion of the PRLR in the pancreas that show reduced islet number and β-cell mass, but normal glucose levels and tolerance (8). This evidence concerns the gene INS and Glucose intolerance.