HK2 and cancer: In human non-oncocytic thyroid cancers, clinical data show higher concentrations of lactate [19,20,21,22,23,24,25] and higher expression levels of the glycolysis-related molecules, such as GLUT1, HK2, LDHA and MCT1 and 4 (these isotypes are frequently over-expressed in cancers), than normal counterparts [26,27,28,29,30,31]; these are especially evident in cancers from aged patients [32].