Diabetes
mellitus is a common chronic metabolic disorder with loss of the normal
control of fuel use and storage, particularly affecting the sugar
glucose. It causes typical symptoms and complications. Diabetes is
important because of the consequences for people, who have it, and for
their families. The number of new cases of diabetes is increasing
rapidly. In the past, diabetes has been seen as leading to disability
and premature death, but now increased understanding of the underlying
disease process and advances in screening for and treatment of
complications now means that disability is no longer inevitable. This
site outlines the current concepts in the knowledge of the cause of
diabetes, changes in diagnostic classification, current treatments and
possible future developments in this important and rapidly advancing
field of medicine.
Classification of Diabetes
The
term “diabetes mellitus” describes the various clinical syndromes that
present with raised blood glucose. It has a variety of causes, and
affects the metabolism of not only glucose, but also other body fuels
such as ketone bodies, fats and cholesterol. Over the years there have
been many changes in the classification of diabetes. This is now
largely settled with the 1997 American Diabetes Association/World
Health Organisation following definitions. Insulin-dependent, formerly
juvenile onset diabetes is now known as Type 1. Non-insulin dependent
or maturity onset diabetes is now classified as Type 2. Diabetes
induced by other causes is classified as secondary diabetes.
Type 1 Diabetes
Type
1 diabetes presents most commonly in an acute form with very raised
blood glucose, which causes a severe thirst with large quantities of
urine and dehydration. There is weakness and weight loss. As it
progresses, there is a marked disturbance of the body chemistry known
as acidosis. Fat breakdown shows as the characteristic smell on the
breath of ketones, and these can be measured in the urine with a test
strip. Left untreated, this results in death, and this was always the
case prior to the introduction of insulin by the Canadians, Banting and
Best in 1922. Type 1 diabetes most frequently presents in childhood or
young adulthood, but it can occur at any age. The incidence of this
type of diabetes is increasing, and it is of concern that this increase
is most marked in the very young. In Type 1 diabetes, insulin
production from the pancreas is much reduced and may be absent. It is
now thought that Type 1 diabetes is caused by an abnormal immune
response with destruction of the beta cells of the islets of
Langerhans. The onset of inflammation and destruction of the
pancreatic cells starts some time before the clinical onset of the
disease. Only certain people with specific immunological markers
appear to be prone to the development of Type 1 diabetes. However,
many people with apparent genetic susceptibility to Type 1 diabetes do
not go on to develop diabetes. It is therefore clear that other
factors must act to precipitate pancreatic destruction. Many factors
have been postulated as being the trigger of Type 1 diabetes. Suggested trigger factors include infection with Coxsackievirus B, or
other virus, early exposure to cows milk, early weaning or dietary
deficiency of certain trace elements. However, none of these proposed
triggers to the autoimmune response has been proven at present. Once
the inflammation of the islet cells occurs, there is irreversible
destruction of these cells leading to the clinical syndrome. At
presentation, the only treatment available for Type 1 diabetes is insulin replacement.
Type 1 diabetes is insulin replacement.38803
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Type 2 Diabetes
The
majority of people with Type 2 diabetes may have few symptoms. The
level of fasting blood sugar levels within a population is distributed
as a continuum. At either end of this scale it is clear to state who
has diabetes and who does not. The challenge has therefore been to
describe the point on the continuum, which is associated with the
future development of diabetic complications. Type 2 diabetes is now
diagnosed by the presence of a fasting blood sugar of greater than 7
mmol, or a random blood sugar of greater than 11 mmol. Again, knowledge
about the aetiology of this type of diabetes has also increased over
recent years. Study of the molecular structure and function of cells
and their genetic code has demonstrated a huge number of potential
defects at almost every point of insulin production, release and
action. These defects lead to the common presenting features of Type 2
diabetes. The majority of cases of Type 2 diabetes are caused by a
decline in insulin production. This decline in pancreatic function is
slow, and appears not to be autoimmune in origin. It may be associated
with resistance to the effect of insulin at muscle and at the liver. This insulin resistant form of diabetes frequently occurs in the
classic triad of obesity, hypertension and hypercholestrolemia, and is
particularly associated with premature death from cardiovascular
causes. As with Type 1 diabetes, the tendency to develop Type 2
diabetes is also largely inherited. Diabetes may be precipitated by
obesity, reduced physical activity and increasing age. As a result of
changes in behaviour of the population as a whole, the prevalence of
Type 2 diabetes is increasing throughout the world. It is estimated
that between 3 and 4 million people in the UK will have Type 2 diabetes
by 2010.
Type 2 diabetes is treated by a combination of diet, exercise, tablets and eventually insulin
Other Forms of Diabetes
Other
causes of diabetes include, diseases of the pancreas, other hormone
diseases including acromegaly, Cushing's syndrome and disease and the
use of steroids medication. Diabetes can present and complicate the
later part of pregnancy, this gestational diabetes, which resolves at
delivery, may represent as Type 2 diabetes later in life. Finally,
there is a subset of cases of diabetes in the young, who have
abnormalities of insulin production and secretion or defects of
recognition of blood sugar level. These are known as maturity onset
diabetes of the young (MODY). These cases may initially thought to be
Type 1 diabetes, but can be treated with insulin.