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Diabetes Mellitus

Diabetes Mellitus 

Definition - Causes and types 
Pathogenesis of diabetes mellitus

Definition 

Diabetes Mellitus  is one of endocrine diseases of the pancreatic origin characterized by chronic disorder in carbohydrates , fat and protein metabolism . The fundamental defect in diabetes mellitus is an absolute or relative lack of insulin . 


Causes and Types

1 - Absolute lack of insulin due to destruction of beta cells in islets of langerhans , which are responsible for insulin production . This form of diabetes is called Juvenile onset diabetes mellitus , usually occurred in young . Destruction of beta cells of the pancreas usually occurred in pancreatitis , where the diabetes mellitus is a common sequel .It is also called Type1 diabetes or insulin dependent diabetes mellitus .




2 - Relative lack of insulin or decrease of insulin response due to decrease of insulin receptors on the target cells .This type is usually occurred in adults or mature individuals especially obese ones and is called maturity onset diabetes mellitus or type2 diabetes .In this form of diabetes , insulin is in the normal level , but tissues not respond to its action , so that , This form of diabetes mellitus is called non insulin dependent diabetes mellitus . 








3 - Excess of corticosteroids , ACTH , growth hormone has a diabetogenic influence , as they increase glucose in the blood and a case of hyperglycemia or diabetic reaction is developed

4 - Miscellaneous influences such as : 
a- Pregnancy 
b- Stress reaction 


Pathogenesis of diabetes mellitus 

Deficiency of insulin cause increase of glucose level in the blood because tissues are unable to utilize glucose . So that , body use other sources of energy form fat and protein causing increase of gluconeogenesis and increase destruction and hydrolysis of body fat , which leads to production of large amount of ketone bodies  such as acetone , acetoacetic acid  and Beta hydroxy butyric acid .Increase glucose and ketones cause hyperglycemia and ketonemia  , and when it exceeds the renal threshold , it will cause glucosuria and ketonuria .

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