5372 lecture 2

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Diabetes mellitus

Dr. Essam H. Jiffri

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Introduction

- Diabetes mellitus is a heterogeneous group of disorders characterized by hyperglycaemia, glycosuria and associated abnormalities of lipid and protein metabolism.

-It is common, affecting up to 2% of Westem populations, 17% in Saudi Arabia.

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Introduction-Insulin metabolism is abnormal in diabetes, either

because of:• reduced secretion or• to insensitivity to its effects.

-Two main types of Diabetes: • Insulin-dependent (IDDM or type 1 diabetes

mellitus, formerly juvenile-onset)• Non-insulin-dependent (NIDDM or type 2

diabetes mellitus, formerly maturity onset)

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Classification of diabetes mellitus

Insulin -Dependent

(Type I )Diabetes

Non-Insulin-Dependent

(Type 2 )Diabetes

MalnutritionRelated

Diabetes Mellitus

ImpairedGlucoseTolerance Gestational

Diabetes Mellitus

SecondaryDiabetes

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1 -Insulin- Dependent )Type I( Diabetes

-Insulin secretion is absent or severely reduced in IDDM as a result of immunological destruction of beta- cells in the islets of Langerhans.

-Circulating islet cell antibodies are found in the majority of patients at presentation and infiltration of the islets by T lymphocytes also occurs.

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-Genetic factors are important in the development of IDDM-individuals with human leukocyte antigen (HLA) system antigens DR3 and DR4 have increased susceptibility for IDDM.

-The environmental event effects, usually a viral infection, particularly with:

• Coxsackie B4 or• mumps.

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-Most cases of IDDM present before 30 years of age.

-The clinical presentation is often acute, with polyuria, polydipsia, polyphagia, weight loss and tiredness developing over several days and ketosis may be present.

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2-Non-Insulin-Dependent )Type 2( Diabetes

-Non-insulin-dependent diabetes is a heterogeneous group of disorders in which several features contrast with those found in IDDM.

-NIDDM has been divided by the World Health Organization (WHO) into two main groups:

• Obese• Non-obese

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- Insulin secretion is retained, although it is inadequate to control blood glucose levels.

- There is resistance to the effects of insulin in due to reduced insulin receptors

-Genetic factors are a more important aetiological factor in NIDDM than IDDM.

-Identical twins have a near 100% chance and the risk of developing NIDDM is higher than IDDM if a parent has the disease.

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-There are no HLA associations and no islet cell antibodies are found.

- Not all patients with NIDDM are over weight, there is a clear association with obesity.

- Obese patients develop NIDDM either have:• diminished pancreatic reserve or• a secretory defect in the pancreatic beta-

cells

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-Clinical onset is usually in middle age and the prevalence increases with age.

- NIDDM is often detected by urine testing during a routine medical examination.

- Patients may complain of polyuria and polydipsia, ketosis is rare.

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3- Malnutrition-Related Diabetes Mellitus

-Found mainly in developing countries due to protein-deficient diabetes.

-The aetiology of these is not clear.

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4- Diabetes Associated with Other Disorders )Secondary Diabetes(

- Diabetes may occur in association with other conditions, particularly pancreatic disorders such as:

• chronic pancreatitis

• haemochromatosis may cause destruction of beta-cells.

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4- Diabetes Associated with Other Disorders )Secondary Diabetes(

-Endocrinopathies (endocrine disorders) which result in:

- increased secretion of counter-regulatory hormones can induce insulin resistance.

-Diabetes occurs in association with several genetic disorders, including:

• Turner's syndrome

• Down's syndrome

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5- Gestational Diabetes Mellitus

- Gestational diabetes occurs for the first time in pregnancy.

- Glycosuria is common because the renal threshold for glucose is exceeded.

- Complications can occur due to blood glucose concentrations in both mother and fetus.

- Glucose tolerance reverts to normal after delivery in most cases many later develop frank diabetes.

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6- Impaired Glucose Tolerance

-Impaired glucose tolerance (IGT) is an asymptomatic condition

-Diagnosed on the basis of the response of blood glucose to the ingestion of a standard oral glucose solution (oral glucose tolerance test, OGTT; 75g anhydrous sugar in 300 ml water, blood and urine samples taken at 2h).

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KEY POINTS

Type 1 diabetes mellitus is characterizedby insulin deficiency

-Type 2 diabetes mellitus is characterized-by insulin resistance

-Diabetes mellitus is diagnosed by -clinical features and blood glucose

- measurements or an oral glucose tolerance test .

5372 lecture 2

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