DEFINITION AND DESCRIPTION OF DIABETES MELLITUS
Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia..." />
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DEFINITION AND DESCRIPTION OF DIABETES MELLITUS
Diabetes mellitus is a group of metabolic diseases
characterized by hyperglycemia resulting from defects in insulin
secretion, insulin action, or both. The chronic hyperglycemia of
diabetes is associated with long-term damage, dysfunction, and
failure of various organs, especially the eyes, kidneys, nerves,
heart, and blood vessels. Several pathogenic processes are
involved in the development of diabetes. These range from
autoimmune destruction of the cells of the pancreas with
consequent insulin deficiency to abnormalities that result in
resistance to insulin action. The basis of the abnormalities in
carbohydrate, fat, and protein metabolism in diabetes is
deficient action of insulin on target tissues. Deficient insulin
action results from inadequate insulin secretion and/or
diminished tissue responses to insulin at one or more points in
the complex pathways of hormone action. Impairment of insulin
secretion and defects in insulin action frequently coexist in the
same patient, and it is often unclear which abnormality, if
either alone, is the primary cause of the hyperglycemia. Symptoms
of marked hyperglycemia include polyuria, polydipsia, weight
loss, sometimes with polyphagia, and blurred vision. Impairment
of growth and susceptibility to certain infections may also
accompany chronic hyperglycemia. Acute, life-threatening
consequences of uncontrolled diabetes are hyperglycemia with
ketoacidosis or the nonketotic hyperosmolar syndrome. Long-term
complications of diabetes include retinopathy with potential loss
of vision; nephropathy leading to renal failure; peripheral
neuropathy with risk of foot ulcers,
amputations, and Charcot joints; and autonomic neuropathy causing
gastrointestinal, genitourinary, and cardiovascular symptoms and
sexual dysfunction. Patients with diabetes have an increased
incidence
of atherosclerotic cardiovascular, peripheral arterial, and
cerebrovascular disease. Hypertension and abnormalities of
lipoprotein metabolism are often found in people with
diabetes.
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 sufficient 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. The degree of hyperglycemia (if any)
may change over time, depending on the extent of the underlying
disease process (Fig. 1). A disease process may be present but
may not have progressed far enough to cause hyperglycemia. The
same disease process can cause impaired fasting glucose (IFG)
and/or impaired glucose tolerance (IGT) without fulfilling the
criteria
for the diagnosis of diabetes. In some individuals with diabetes,
adequate glycemic control can be achieved with weight reduction,
exercise, and/or oral glucoselowering agents. These individuals
therefore
do not require insulin. Other individuals who have some residual
insulin secretion but require exogenous insulin for adequate
glycemic control can survive without it. Individuals with
extensive -cell destruction and therefore no residual insulin
secretion require insulin for survival. The severity of the
metabolic abnormality can progress, regress, or stay the same.
Thus, the degree of hyperglycemia
reflects the severity of the underlying metabolic process and its
treatment more than the nature of the process itself.
Enviado por Mario Unigarro
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