Collectively these tissues of expression correlate well with current hypotheses that INSL5 a) is a gut hormone that modulates glucose metabolism either directly or indirectly via gluconeogenesis (6–8); b) is an orexigenic hormone that influences satiety, through both gut-nervous system and hypothalamus-cerebellum cross-talk with RXFP4 (9); c) plays roles in female and male fertility (6, 10, 11), and d) together with RXFP4, are markers of colorectal and breast cancer progression (12–15). This evidence concerns the gene RXFP4 and breast carcinoma.