Crustacean hyperglycemic hormone (CHH) is a peptide hormone originally identified in the X-organ/sinus gland (XO/ SG) complex of the eyestalks. It belongs to the CHH family which also includes molt-inhibiting hormone (MIH), vitellogenesis-inhibiting hormone (VIH), and mandibular organ-inhibiting hormone (MOIH), and ion transport peptide (ITP). Multiple molecular variants of CHH are generated by both post-transcriptional and post-translational mechanisms. In addition to the XO/SG complex, CHH gene is widely expressed in many extra-eyestalk tissues. Functionally, available data indicate that CHH is involved with the regulation of carbohydrate metabolism and stress-induced hyperglycemia. Several other physiological processes, including molting, ion and water balance, reproduction, and immunity, are likely also regulated by CHH. The functional role(s) of the alternatively splice form CHH-like peptide (CHH-L) are different from those of CHH and remain unknown. Combined results showed that cyclic guanosine 3',5'-monophosphate (cGMP) plays important roles in mediating the effects of CHH on carbohydrate metabolism. Recent studies of receptor guanylyl cyclase (rGC) may lead to characterization and identification of CHH receptor(s). Future efforts are needed to fully understand the functional roles of the different CHH variants; identification of CHH receptor(s) hold the promise of revealing in greater depth the structure/functional relationships of the various structural variants.