Diabetes mellitus is a clinical syndrome characterized by hyperglycemia due to insulin deficiency or resistance. There are several types of diabetes classified based on etiology. Type 1 diabetes is caused by autoimmune destruction of pancreatic beta cells leading to insulin deficiency. Type 2 diabetes results from insulin resistance and inadequate compensatory insulin secretion. Tests used to diagnose diabetes include fasting plasma glucose, A1c hemoglobin, and oral glucose tolerance test. Elevated levels on these tests indicate hyperglycemia and a diagnosis of diabetes.

1. Diabetes mellitus
by Najiur Ruman
1. Introduction:
Diabetes mellitus is a clinical syndrome characterized by the hyperglycemia due to
absolute or relative deficiency of insulin , i.e due to either A deficiency are insulin
secretion or a combination of insulin resistance and inadequate insulin secretion to
compensate. diabetes is the most common endocrine disorder. It affects almost all
the system of the human body since lack of insulin affect metabolism of
carbohydrate protein and fat and also causes a significant disturbance in water and
electrolyte balance.
2. Classification of diabetes mellitus:
A. Type 1( insulin dependent Diabetes mellitus IDDM )
1. immune mediated
2. Idiopathic
B. type 2 (non insulin dependent Diabetes mellitus NIDDM)
1. Non obese type 2
2. Obose type 2
C. Other specific types of diabetes
1. genetic defects of pancreatic Beta cell function
a. maturity onset diabetes of young MOD Y 1-6 . A rare subgroup, Belongs
two type 2 diabetes
b. Diabetes mellitus associated with a mutation of mitochondrial DNA
2. genetic defects of insulin action
a. type a insulin resistance
b. Leprechaunism
c. rabson manhandle syndrome
d. lipoatrophic diabetes
3. Diabetes due to pancreatic diseases (exocrine part)
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2. 4. Endocrinopathies (i.e execess endogenous production of hormonal
antagonists to insulin)
5. Drug a chemical induced diabetes
6. Diabetes due to viral infections (e.g congential rubella, mumps, Coxackie
virus B)
7. Uncommon forms of immune mediated diabetes
8. diabetes associated with the genetic syndromes ( e .g down syndromes,
turner's syndrome, otic atropy, Diabetes mellitus, nerve defences, myotonic
dystrophy)
D. Gestational diabetes
2.1 Type 1 Diabetes mellitus
Type 1 Diabetes mellitus occurs due to pancreatic beta cell destruction
predominantly by
i. An auto email process greater than 90% and less commonly by ii. idiopathic
unknown causes less than 10%. the immune mechanism involved in Type 1
Diabetes in a slow t cell mediated auto immunity. about one third of these at due to
genetic linkage with special predisposition of human Lymphocytes antigen
(HLA).The particular haplotypes associate with Type 1 Diabetes are HLA-DR3
and HLA-DR4. Some viral infections also known to causes autoimmune damage to
beta cells.
Type 1 Diabetes occurs mainly in the Juvenile age group with highest incidence in
between 10 to 14 years specially in the known of pace and rarely occurs in the
adult life.It is usually associated with the ketoacidosis if not treated duly. in Type 1
Diabetes circulating insulin is almost absent plasma glucagon elevated part the
pancreatic beta cell failed to respond to all insulinogenic stimauli.As a result
insulin supplementation is essentially required to reverse this catabolic state reduce
blood glucose prevent ketoacidosis and reduce the plasma glucagon.
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3. 2.2 Type 2 Diabetes mellitus:
Type 2 Diabetes mellitus is the most prevent from of diabetes greater than 90%
,results from insulin resistance a defect in compensatory insulin secretion.It
representsheterogeneous group comprising milder forms of diabetes that occur
permanently in adults (most are over 40 years)But occasionally in juveniles. in this
insulin production by Beta cells a significant to prevent ketoacidosis but not
adequate to prevent hyperglycemia in the face of increased needs owing to tissue
insensitivity. Although in most cases of type 2 diabetes causes is and on several
interrelated factors are considered responsible for developing tissue resistant to
insulin and impaired beta sale response to glucose such as a living a sanitary
lifestyle and the abdominal obesity in addition of eating especially fine come. With
the obesity and under activity contribute to aggravate the hyperglycemia. A strong
genetic influence with positive family history has also been established in
developing type 2 diabetes by different epidemiologic studies. Repeated pregnancy
may also contribute to cause type 2 diabetes.
3. Clinical features:
3.1 ​Presentations:
1. Many patients are first noted to have glycosuria in In the course of some
routine
examinations. They may have had few or no symptoms and no abnormal
physical signs.
2. Some patients present with the classical symptoms of diabetes example
thirst, polydipsia, polyuria, nocturia, tiredness, loss of weight, white marks
on the clothing, pruritus vulvac or balanitis, impotence, myopia, and
paraesthesia in the limbs.
3. Diabetes may first present as a fulminating ketoacidosis associated with an
acute infection and in such cases epigastric pain and vomiting may be the
presenting complaints.
4. Patient may present with symptoms due to the complications of diabetes.
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4. 3.2 Physical signs:
Cases without complications will usually show no abnormal physical signs. In
some cases vulvitis or balanitis may be found. In the fulminating case the most
striking features are those of dehydration. The intra ocular pressure may be
obviously reduced. A rapid pulse and a low blood pressure found. Breathing may
be deep and sighing in the acidotic patient , the breath is usually foetid and the
stickly sweet smell of acetone may be noticeable.
Apathy and confusion may be found or there may be stupor or even coma.
Evidences of complications of diabetes may be noted e.g. diabetic retinopathy,
diabetic neuropathy, loss of ankle jerks and impaired vibration sense in the legs.
3.3 Investigations:
1. Urine testing – (urineshould be taken 2 hours after meal)
i . Glycosuria – a positive response indicates that the urinary glucose
concentration exceeds 10-20 mg/100ml
ii . Detection of keton bodies in urine.
2. Random blood sugar – a random blood sugar exceeding 250mg/100ml (14
mmol/l) is almost certain to diagonse diabetes.
3. Oral glucose tolerance test- a fasting glucose level avobe 120mg/100ml or a
glucose level above 180mg/100ml 2 hours after glucose indicated diabetes.
4. Glycated haemoglobin becomes glycated by slow non-enzymatic ketoamine
reactions between glucose and other sugars and the free amino groups on the α and
β chains of hemoglobin. The major form of glycated haemoglobin (HbA​1​) is
hemoglobina A​1c​ (HbA​1c​) where glucose is the carbohydrate. HbA​1c​ compries 4-6%
of total glycated hemoglobin (HbA​1​). The hemoglobin A​1c​ fraction is abnormally
elevated in diabetic persons with chronic hyperglycemia. The rate of formulation
of HbA​1c​ is directly proportional to ambient blood glucose concentration , a rise of
1% in HbA​1c​ corresponds to an approximate average increase of 2mmol/l
(36mg/dl) in blood glucose. The assesment of glycated haemoglobin provides an
accurate measure of glycaemic control over a period of weeks to months in a
known diabetic patient.
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4. Tests are used to diagnose diabetes and prediabetes:
Health care professionals most often use the fasting plasma glucose (FPG) test or
the A​1c​ test to diagnose diabetes. In some cases, they may use a random plasma
glucose (RPG) test.
4.1 Fasting plasma glucose (FPG) test:
The FPG blood test measures your blood glucose level at a single point in time. For
the most reliable results, it is best to have this test in the morning, after you fast for
at least 8 hours. Fasting means having nothing to eat or drink except sips of water.
4.2 A​1c​ test
The ​A​1c​ test​ is a blood test that provides your average levels of blood glucose over
the past 3 months. Other names for the A​1c​ test are hemoglobin A​1c ​, HbA​1c ​,
glycated hemoglobin, and glycosylated hemoglobin test. We can eat and drink
before this test. When it comes to using the A​1c​ to diagnose diabetes, the doctor
will consider factors such as our age and whether we have ​anemia​ or another
problem with our blood. The A​1c​ test is not accurate in people with anemia.
If the ​African, Mediterranean, or Southeast Asian descent, A​1c​ test results may be
falsely high or low​. The health care professional may need to order a different type
of A​1c​ test.
The health care professional will report A​1c​ test result as a percentage, such as an
A​1c​ of 7 percent. The higher the percentage, the higher average blood glucose
levels.
People with diabetes also use information from the A​1c​ test to help ​manage their
diabetes​.
4.3 Random plasma glucose (RPG) test:
Sometimes health care professionals use the RPG test to diagnose diabetes when
diabetes symptoms are present and they do not want to wait until you have fasted.
You do not need to fast overnight for the RPG test. You may have this blood test at
any time.
4.4 Tests are used to diagnose gestational diabetes:
Pregnant women may have the glucose challenge test, the oral glucose tolerance
test, or both. These tests show how well your body handles glucose.
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6. 4.5 Glucose challenge test:
If anyone pregnant and a health care professional is checking her for gestational
diabetes, she may first receive the glucose challenge test. Another name for this
test is the glucose screening test. In this test, a health care professional will draw
her blood 1 hour after drink a sweet liquid containing glucose. She does not need to
fast for this test. If her blood glucose is too high—135 to 140 or more—she may
need to return for an oral glucose tolerance test while fasting.
4.6 Oral glucose tolerance test (OGTT)
The OGTT measures blood glucose after fast for at least 8 hours. First, a health
care professional will draw blood. Then the person will drink the liquid containing
glucose. For diagnosing gestational diabetes, he will need your blood drawn every
hour for 2 to 3 hours.
High blood glucose levels at any two or more blood test times during the
OGTT—fasting, 1 hour, 2 hours, or 3 hours—mean he has gestational diabetes.
The health care team will explain what OGTT results mean.
Health care professionals also can use the OGTT to diagnose type 2 diabetes and
prediabetes in people who are not pregnant. The OGTT helps health care
professionals detect type 2 diabetes and prediabetes better than the FPG test.
However, the OGTT is a more expensive test and is not as easy to give. To
diagnose type 2 diabetes and prediabetes, a health care professional will need to
draw blood 1 hour after drink the liquid containing glucose and again after 2 hours.
Fig.: Interpretation of OGTT
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