The vast majority of cases of diabetes
fall into two broad etiopathogenetic categories
(discussed in greater detail below).
In one category, type 1 diabetes, the cause
is an absolute deficiency of insulin secretion.
Individuals at increased risk of developing
this type of diabetes can often be
identified by serological evidence of an
autoimmune pathologic process occurring
in the pancreatic islets and by genetic
markers. In the other, much more prevalent
category, type 2 diabetes, the cause is
a combination of resistance to insulin action
and an inadequate compensatory insulin
secretory response.In the latter
category, a degree of hyperglycemia suffi-
cient to cause pathologic and functional
changes in various target tissues, but
without clinical symptoms, may be
present for a long period of time before
diabetes is detected. During this asymptomatic
period, it is possible to demonstrate
an abnormality in carbohydrate
metabolism by measurement of plasma
glucose in the fasting state or after a challenge
with an oral glucose load.