The problem of treating diabetes mellitus seemed to have been solved by the discovery of insulin and the production of purified crystalline insulin compounds, whose time of effect can be varied by using different additions. Researchers have been searching for orally applicable substances to reduce blood sugar levels in order to free diabetics from the necessity of daily injections. There are also other reasons for this research. Pathophysiological investigations in diabetes mellitus have shown that metabolic errors are not always based on a simple insulin deficiency, but that in many cases other insulin antagonistic factors play a part. For instance, the concept of deficiency diabetes growth-onset type, usually found in juveniles and ectomorphs, was contrasted with the concept of hypertensive diabetes or "counterregulatory diabetes.".