These extra-bone functions include the following: (1) influencing brain development and function, which sheds new light on the cause of cognitive decline with age [107]; (2) stimulating the expression of cyclin D1 and insulin in pancreatic β cells and adiponectin (an insulin-sensitizing adipokine) in adipocytes and improving glucose tolerance [108]; (3) linking the pathway between central obesity and insulin resistance [109]; and (4) promoting male fertility by increasing testosterone production [110,111]. Here, INS is linked to Insulin resistance.