Diabetes mellitus is a condition of chronically elevated blood glucose concentrations.
which give rise to its main symptom of passing large quantities of sweet – tasting urine ( diabetes from the Greek word meaning ‘ a siphon ’.
As the body acts as a conduit for the excess fl uid, and mellitus from the Greek and Latin for honey).
The fundamental underlying abnormality is a net (relative or absent) defi ciency of the hormone insulin. Insulin is essentially the only hormone that can lower blood glucose.
There are two categories of diabetes:
type 1 is caused by an autoimmune destruction of the insulin – producing β cell of the islets of Langerhans in the pancreas (absolute.defi ciency);
type 2 is a result of both impaired insulin secretion and resistance to its action – often secondary to obesity (relative deficiency).
The precise level of blood glucose that defi nes diabetes has been revised several times. and is covered in more detail in
Diabetes is common and is becoming more
common. Age – adjusted prevalence is set to rise from 5.9% to 7.1% (246 – 380 million) worldwide in the 20 – 79 year age group, a 55% increase (Figure 1.1 ). The relative proportions of type 1 to type 2 vary from 15 : 85 for Western populations
to 5 : 95 in developing countries.
It is the short – and long – term complications of diabetes which make it a major public health problem.
Absolute defi ciency of insulin leads to ketoacidosis and coma with an
appreciable mortality even in the UK and other Western countries.
Hyperglycaemic hyperosmolar coma (now called hyperglycaemic hyperosmolar state) is less common and more insidious but remains an equally serious problem for
people with type 2 diabetes .