Despite intense scrutiny the precise etiology of diabetes mellitus remains unclear. There appear to be two major forms of diabetes: juvenile-onset or insulin-dependent diabetes, and late-onset or insulin-independent diabetes; the late-onset form, in itself, may be etiologically heterogeneous. Either form may occur at any age, with a clear distinction between the two often being difficult to make. Juvenile-onset diabetes, representing 5% to 10% of all cases, is characterized by abrupt onset, clinical manifestation of hyperglycemia and ketoacidosis, and generally by a requirement for exogenous insulin; in maturity-onset diabetes plasma levels of insulin are usually normal or elevated and the abnormality in glucose metabolism results from a decrease in the number of insulin receptors rather than a deficiency of the hormone itself
