As per the WHO,
Diabetes mellitus (DM) is defined as a hetrogeneous metabolic disorder characterised by common feature of chronic hyperglycaemia with disturbance of carbohydrate, protein metabolism.
At this point, it is also important to understand another related term, metabolic syndrome (also
called syndrome X or insulin resistance syndrome), consisting of a combination of metabolic TYPE 2 DM This type comprises about 80% cases of DM.
It was previously called maturity-onset diabetes, or non-insulin dependent diabetes mellitus (NIDDM) of obese and non-obese type.
Although type 2 DM predominantly affects older individuals, it is now known that it also occurs in obese adolescent children;
Hence the term MOD for it is inappropriate.
Moreover, many type 2 DM patients also require insulin therapy to control Hyperglycaemia or to prevent ketosis and
Thus are not truly non-insulin dependent contrary to its older nomenclature.
OTHER SPECIFIC ETIOLOGIC TYPES OF DM
Besides the two main types, about 10% cases of DM have a known specific etiologic defect listed in Table 25.4. One important subtype abnormalities which increase the risk to develop diabetes mellitus and cardiovascular disease.
Major features of metabolic syndrome are-
DM is a leading cause of morbidity and mortality world over. It is expected to continue as a major health problem owing to its serious complications, especially end-stage renal
disease, IHD, gangrene of the lower extremities, and blindness
in the adults.
Top 5 countries with highest prevalence of DM are
India, China, US, Indonesia and Japan.
In India, its incidence is estimated at 7% of adult population (approximately 65 million
affected people), largely due to genetic susceptibility combined with changing life style of low-activity high-calorie diet in the growing Indian middle class. The incidence is somewhat low in
Africa. But prevalence of DM is expected to rise in developing countries of Asia and Africa due to urbanisation and associated obesity and increased body weight.
The rise in prevalence is more for type 2 diabetes than for type 1.
It is anticipated that by the year 2030 the number of diabetics globally will double from
the present figure of 250 million.
CLASSIFICATION AND ETIOLOGY
The older classification systems dividing DM into
undergone major revision due to extensive understanding of etiology and pathogenesis of DM in recent times.
As outlined in Table 25.4,
Current Classification of DM based on etiology divides it into two broad categories—
Type 1and Type 2;
besides there are a few uncommon specific etiologic types, and gestational DM.
American Diabetes Association (2007) has identified risk factors for type 2 DM listed in
Table 25.5.
Brief comments on etiologic terminologies as contrasted
with former nomenclatures of DM are as under:
TYPE 1 DM It constitutes about 10% cases of DM. It was
previously termed as juvenile-onset diabetes (JOD) due to its
occurrence in younger age, and was called insulin-dependent
DM (IDDM) because it was known that these patients have
absolute requirement for insulin replacement as treatment.
However, in the new classification, neither age nor insulin-
dependence are considered as absolute criteria. Instead, based
on underlying etiology,
Type 1 DM is further divided into 2 subtypes:
Subtype 1A (immune-mediated)
DM characterised by " autoimmune destruction of β-cells which usually leads to insulin
deficiency."
Subtype 1B (idiopathic)
DM characterised by "insulin deficiency with tendency to develop ketosis but these patients
are negative for autoimmune markers."
Though type 1 DM occurs commonly in patients under 30
years of age, autoimmune destruction of β-cells can occur at
any age. In fact, 5-10% patients who develop DM above 30 years
of age are of type 1A DM and hence the term JOD has becomeTYPE 2 DM This type comprises about 80% cases of DM. It was previously called maturity-onset diabetes, or non-insulin
dependent diabetes mellitus (NIDDM) of obese and non-
obese type.
Although type 2 DM predominantly affects older individuals,
it is now known that it also occurs in obese adolescent children;
hence the term MOD for it is inappropriate. Moreover, many
type 2 DM patients also require insulin therapy to control
hyperglycaemia or to prevent ketosis and thus are not truly
non-insulin dependent contrary to its older nomenclature.
OTHER SPECIFIC ETIOLOGIC TYPES OF DM
Besides the two main types, about 10% cases of DM have a known specific
etiologic defect listed in Table 25.4. One important subtype
Diabetes mellitus (DM) is defined as a hetrogeneous metabolic disorder characterised by common feature of chronic hyperglycaemia with disturbance of carbohydrate, protein metabolism.
At this point, it is also important to understand another related term, metabolic syndrome (also
called syndrome X or insulin resistance syndrome), consisting of a combination of metabolic TYPE 2 DM This type comprises about 80% cases of DM.
It was previously called maturity-onset diabetes, or non-insulin dependent diabetes mellitus (NIDDM) of obese and non-obese type.
Although type 2 DM predominantly affects older individuals, it is now known that it also occurs in obese adolescent children;
Hence the term MOD for it is inappropriate.
Moreover, many type 2 DM patients also require insulin therapy to control Hyperglycaemia or to prevent ketosis and
Thus are not truly non-insulin dependent contrary to its older nomenclature.
OTHER SPECIFIC ETIOLOGIC TYPES OF DM
Besides the two main types, about 10% cases of DM have a known specific etiologic defect listed in Table 25.4. One important subtype abnormalities which increase the risk to develop diabetes mellitus and cardiovascular disease.
Major features of metabolic syndrome are-
- Central obesity,
- Hypertriglyceridaemia,
- Low LDL cholesterol,
- Hyperglycaemia
- Hypertension.
DM is a leading cause of morbidity and mortality world over. It is expected to continue as a major health problem owing to its serious complications, especially end-stage renal
disease, IHD, gangrene of the lower extremities, and blindness
in the adults.
Top 5 countries with highest prevalence of DM are
India, China, US, Indonesia and Japan.
In India, its incidence is estimated at 7% of adult population (approximately 65 million
affected people), largely due to genetic susceptibility combined with changing life style of low-activity high-calorie diet in the growing Indian middle class. The incidence is somewhat low in
Africa. But prevalence of DM is expected to rise in developing countries of Asia and Africa due to urbanisation and associated obesity and increased body weight.
The rise in prevalence is more for type 2 diabetes than for type 1.
It is anticipated that by the year 2030 the number of diabetics globally will double from
the present figure of 250 million.
CLASSIFICATION AND ETIOLOGY
The older classification systems dividing DM into
- primary (idiopathic)
- secondary types,
- juvenile-onset and
- maturity onset types,
- insulin-dependent (IDDM)
- non-insulin dependent (NIDDM) have become obsolete and
undergone major revision due to extensive understanding of etiology and pathogenesis of DM in recent times.
As outlined in Table 25.4,
Current Classification of DM based on etiology divides it into two broad categories—
Type 1and Type 2;
besides there are a few uncommon specific etiologic types, and gestational DM.
American Diabetes Association (2007) has identified risk factors for type 2 DM listed in
Table 25.5.
Brief comments on etiologic terminologies as contrasted
with former nomenclatures of DM are as under:
TYPE 1 DM It constitutes about 10% cases of DM. It was
previously termed as juvenile-onset diabetes (JOD) due to its
occurrence in younger age, and was called insulin-dependent
DM (IDDM) because it was known that these patients have
absolute requirement for insulin replacement as treatment.
However, in the new classification, neither age nor insulin-
dependence are considered as absolute criteria. Instead, based
on underlying etiology,
Type 1 DM is further divided into 2 subtypes:
Subtype 1A (immune-mediated)
DM characterised by " autoimmune destruction of β-cells which usually leads to insulin
deficiency."
Subtype 1B (idiopathic)
DM characterised by "insulin deficiency with tendency to develop ketosis but these patients
are negative for autoimmune markers."
Though type 1 DM occurs commonly in patients under 30
years of age, autoimmune destruction of β-cells can occur at
any age. In fact, 5-10% patients who develop DM above 30 years
of age are of type 1A DM and hence the term JOD has becomeTYPE 2 DM This type comprises about 80% cases of DM. It was previously called maturity-onset diabetes, or non-insulin
dependent diabetes mellitus (NIDDM) of obese and non-
obese type.
Although type 2 DM predominantly affects older individuals,
it is now known that it also occurs in obese adolescent children;
hence the term MOD for it is inappropriate. Moreover, many
type 2 DM patients also require insulin therapy to control
hyperglycaemia or to prevent ketosis and thus are not truly
non-insulin dependent contrary to its older nomenclature.
OTHER SPECIFIC ETIOLOGIC TYPES OF DM
Besides the two main types, about 10% cases of DM have a known specific
etiologic defect listed in Table 25.4. One important subtype
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