The majority of hormones can be thought of as metabolic in that they produce changes in the rate of metabolism of the target tissues that they affect. This chapter is concerned with peptide hormones released from the corpus cardiacum (CC) which exert specific effects upon intermediary metabolism. Hyperglycemic factors have been reported to exist in the brain-CC complex of insects from most orders. The existence of such factors which can elicit rapid elevations in blood trehalose levels was reported first by J. E. Steele in Periplaneta. Adipokinetic hormone (AKH) is able to induce hyperglycemia in insects other than locusts and it has been of interest to investigate whether the hyperglycemic factors present in Periplaneta and other insects are related structurally to AKH. The hyperglycemic action of CC factors is similar to that of glucagon activation of liver phosphorylase and this similarity has led to the suggestion that glucagon could be the insect hyperglycemic hormone.