Selectively inhibits insulin-stimulated glucose utilization and glycogen deposition in muscle, while not affecting adipocyte glucose metabolism. Interacts with IDE and INS. Abundant in the islets of Langerhans but is not present in the brain or seven other tissues examined. The mature protein is largely unstructured in the absence of a cognate ligand, but contrary to the human protein, it does not easily form fibrillar aggregates. Belongs to the calcitonin family.