Diabetes Mellitus


DIABETES MELLITUS 

Once regarded as a single disease entity, diabetes is now seen as a heterogeneous group of diseases, characterized by a state of chronic hyperglycemia, resulting  from a diversity  of aetiologies,  environmental and genetic, acting jointly.The underlying  cause of diabetes is the defective  production or action of insulin, a hormone that controls glucose, fat and amino acid metabolism. Characteristically,  diabetes is a long _ term disease with variable  clinical  manifestations and progression .Chronic hyperglycemia, from whatever cause, leads to a number of  complications __ cardiovascular, renal, neurological, ocular and others  such as intercurrent  infections.


Classification 

The classification  adopted by WHO is given below  : 




IDDM ( Insulin _ dependent  diabetes  mellitus) is the most severe form of the disease. Its onset is typically  abrupt and  is usually  seen  in individuals less than 30 years of age. It occurs mostly in children,the incidence  is highest among in children, the incidence  is highest among 10_ 14 years old groups, but occasionally  occurs in adults.It is catabolic disorder in which circulating  insulin is virtually absent, plasma glucagon is elevated, and the pancreatic ß cells fail to respon to all insulinogenic stimuli. Exogenous insulin is therefore  required  to reverse the catabolic state, prevent ketosis, reduce the hyperglucagonaemia, and reduce blood glucose. 

  NIDDM is much more common than IDDM. It  is often discovered by chance. It is typically  gradual in onset  and occurs mainly in the middle_ aged and elderly,  frequently mild, slow to ketosis  and is compatible with long survival of given adequate treatment. Its clinical picture is usually complicated  by  the presence of other disease processes. 


 Impaired glucose tolerance ( IGT) describes a state intermediate  __ " at_ risk" group _ between  diabetes mellitus  and normally. It can only be defined  by the oral glucose tolerance test. 

Insulin resistance  syndrome  ( Syndrome X) 

 In obese patients with type 2 diabetes,  the associated  of hyperglycemia, hyperinsulinaemia, dyslipidaemia and hypertension,  which leads to coronary  artery disease and stroke, mayreault from a genetic  defect producing insulin  resistance , with the latter being exaggerated by obesity. It has been proposed that insulin resistance predisposes to hyperglycaemia, which results in hyperinsulinaema. This excessive  insulin level then contributes to high levels  of triglycerides and increased sodium retention by renal tubules , thus inducing  hypertension. 

Epidemiological determinants 

1.AGENT :

  The underlying  cause of diabetes is insulin deficiency  which is absolute  in IDDM and partial in NIDDM. This may be due to a wide variety  of mechanisms:

(a) Pancreatic disorders _ inflammatory,  neoplastic and other disorders  such as cystic fibrosis,  

(b)  Defects in the formation  of insulin, e.g., synthesis of an abnormal,  biologically less active insulin  molecule;

(c) Destruction of beta cells, e.g,. viral infections  and chemical  agents, 

(d) Decreased  insulin sensitivity,  due to decreased  numbers of adipocyte and monocyte insulin  receptors. 

(e) Genetic defects, e.g., mutation of insulin gene; and 

(f) Auto _ immunity. Evidence is accumulating  that the insulin  response to glucose is genetically controlled.  The overall effect of these mechanisms is reduce Utilization of glucose which leads to hyperglycemia accompanied  by glycosuria.

2. HOST FACTORS  

  
(a) AGE: Although diabetes may occur at any age, surveys indicate  that prevalence rises steeply with age. NODDM usually  comes to light  in the middle years  of life and thereafter begins to rise in  frequency.  Malnutrition related diabetes affects large  number of young people. The prognosis is worse in younger diabetics who tend to develop complications earlier  than older diabetics. 

(b) SEX: In some countries  ( e.g., UK) the overall male_ female ratio is about equal. In south _ east Asia, an excess of male diabetics has  been observed, but this is open to questions. 


(c) GENETIC FACTORS: The genetic nature of diabetes  is undisputed. Twin studies showed that in identical  twins who developed  NIDDM, concordance  was approximately 90 per cent, thus demonstrating a strong genetic  component. In IDDM ( type 1 diabetes), the concordance was only about 50 per cent indicating that IDDM is not  totally a genetic  entity. 


(d) IMMUNE MECHANISMS: There is some evidence  of both cell_ mediated  and of humoral activity against  islet cells. Some people appear to have defective  immunological mechanisms,  and  under the influence  of some environmental " trigger ", attack their own insulin producing  cells.

(e) OBESITY : Obseity particularly  central adiposity  has long been accepted as a risk factor for NIDDM and the risk is related to both the duration and degree of obesity. 

(f) MATERNAL  DIABETES  :Offsprings of diabetes  pregnancies including  gestational  diabetes are often large and heavy  at birth, tend to develop  obesity in childhood  and are at high risk  of developing  type 2 diabetes  at an early age. Those born to mothers after they have developed  diabetes have a three_ fold higher risk of developing  diabetes than those born before. Maternal diabetes  associated with low birth weight, when associated  with rapid growth catch _ up later on, appears to increase the risk of subsequent  diabetes  in the child.

3. ENVIRONMENTAL RISK FACTORS 


Susceptibility to diabetes apparatus to be unmasked by a number of environmental factors acting on genetically  susceptible  individuals . They  include: 

(a) SEDENTARY  LIFE STYKE : Sedentary  life style appears  to be an important  risk factor for the development  of   NIDDM. Lack of exercise  may alter the interaction  between  insulin and its receptors  and subsequently  lead to NIDDM. 


(b) DIET : A  high saturated  fat intake  has been associated  with a higher risk of impaired glucose tolerance,  and higher fasting glucose and insulin levels. 


(c) DIETARY FIBRE : In   many  controlled  experimental  studies,  high intakes of dietary  fibre have been shown to result in reduced blood glucose  and insulin  levels in people with type 2 diabetes  and  impaired  glucose tolerance. 

(d) ALCOHOL  : Excessive  intake of alcohol  can increase the risk of diabetes  by damaging  the pancreas  and liver and by promoting  obesity. 

(e) VIRAL INFECTIONS  : Among the viruses that have  been implicated are rubella, mumps,  and human coxsackie virus B4. Viral  infections  may trigger  in immunogenetically susceptible  people  a sequence  of events resulting  in ß _ cell  destruction  .


(f) CHEMICAL  AGENTS  : A number of chemical  agents are known to be toxic to beta cells,  e.g., alloxan, streptozotocin, the rodenticide   VALCOR, etc.A high intake of cyanide producing  foods ( e.g., cassava and certain  beans) may  also have toxic effects on ß _ ces. 


(g) STRESS :  Surgery, trauma, and stress of situations, internal or external,  may  "  bring  out " the  disease. 




 (h) OTHET FACTORS   : High and  low rates of diabetes  have been linked to  a number  of social  factors such  as occupation, marital status, religion,  economic status, education , urbanization  and changes in life style which are elements  of what  is broadly  known as social class. One  of the most important  epidemiological  features  of diabetes  is that it is now common  in the  lower  social classes whereas  50 years ago, the gradient  was the reverse. One reason  could be  rapid changes  in life _ style  in lower cla





SCREENING FOR DIABETES 

1. Urine examination 

      Urine test for glucose, 2 hours after a  meal, is commonly  used in medical  practice for detecting cases of diabetes. All  those with glycosuria are considered  diabetic unless  otherwise proved by a  standard  oral glucose tolerance  test. Most studies now confirm that  although  glucose is found in urine in the most severe  cases of the disease,  and  such  cases  ar likely to be missed by urine test. 

2. Blood sugar testing 


  Because  of the inadequacies of urine examination , " standard  oral glucose test" remains the  cornerstone of diagnosis  of diabetes.  Mass screening  programmes have used glucose measurements of  fasting , post_ prandial  or random blood sample.

   For epidemiological purposes, the 2_ hour value after 75 g oral glucose may be used either alone or  with the fasting  value. Automated biochemistry has now  made  it possible to screen thousands of  samples for glucose estimation. The criteria for the diagnosis of diabetes,  proposed by  WHO.


Target population 

  Screening  of the whole population for diabetes is not considered  a rewarding  exercise. However, screening  of " high_ risk" groups  is considered  more appropriate.  These groups are :

(i) Those  in  the age  group  40  and over 

(ii) Those with a family  history  of diabetes 

(iii) The obese 

(iv) Women who have had a baby weighing  more than 4.5. kg  ( or 3.5. kg  in  constitutionally small populations) 

(v) Women who show excess weight gain during pregnancy, and 

(vi) Parltients with  premature  atherosclerosis.

PREVENTION  AND CARE :

1. Primary prevention :

 Two strategies for primary prevention have been suggested:  (a) Population  strategy , and (b) high _ risk strategy.

a. POPULATION  STRATEGY :

   The scope for primary  prevention of IDDM is limited on the basis of current knowledge  and is probably  not appropriate. However, the development of prevention programmes for NIDDM based on elimination of environmental risk factors is possible. The preventive  measures comprise maintenance of  normal body weight through  adoption of healthy nutritional  habits and physical exercise.  The  nutritional habits include an adequate protein intake,  a high intake of dietary  fiber  and avoidance of sweet foods. 


b. HIGH _ RISK STRATEGY 

    There is no special high_ risk strategy  for IDDM diabetes . At present, there is no practical  justification  for genetic  counselling  as a method  of prevention. 

 Since  NIDDM appears  to be linked  with sedentary   life_ style, over _ nutrition  and  obesity, correction  of  these may reduce  the risk  of  diabetes,  it should be avoided. Subjects at risk should  diabetogenic drugs like oral contraceptives.  It is wise to reduce  factors that promote  atherosclerosis, e.g., smoking , high  blood  pressure, elevated cholesterol  and high triglycerides levels. These programmes may  most effectively be directed  at target  population groups. 

2. Secondary  Prevention:

    When  diabetes  is detected,  it must be  adequately  treated.  The aims  of treatment are:

(a) To  maintain  blood glucose levels as close within the normal limits as is practicable  




(b) To maintain  ideal body weight.  Treatment is based  on (i) Diet alon_ small balanced  meals more frequently, (ii) diet and oral antidiabetic drugs, (iii) diet and insulin. Good control of blood glucose  protects against  the  development  of  complications. 


 Glycosylated  haemoglobin : There should be an estimated  of glycated  ( glycosylated) haemoglobin  at half _ yearly intervals. This  test provides a long _ term index of glucose control.  This test is based on the following  rationale: glucose in  the  blood  is  complexed to a certain  fraction  of haemoglobin  to an extent  proportional  to the  blood  glu concentration.  The percentage  of such glycosylated  haemoglobin reflects the  mean  blood  glucose  levels during  the red cell  life_ time ( e.g., about the  previous  2_ 3 months). 

 
Self _ care : A  crucial  element  in  secondary  prevention  is self  care. That is, the diabetes should take a major  responsibility for  his own care with medical guidance _ e.g., adherence to diet and drug regimens, examination of his own urine and where possible blood glucose  monitoring; self administration of insulin, abstinence from alcohol, maintenance  of optimum weight, attending periodic check_ ups,recognition of symptoms associated  with glucouria and hypoglycemia, etc.

Home blood glucose monitoring:  Assessment of control has been greatly aided by the recent facility of immediate,  reasonable accurate, capillary blood glucose measurements either by one of the many meters now available  or  the direct reading  Haemoglukotest strips. 


 The  patient should  carry  an identification card showing  his name, address, telephone  number and  the  details  of treatment  he is receiving . In  short, he must have a  working knowledge of  diabetes. All these mean education of patients and  their  families  to optimize  the effectiveness  of primary  health care services. 



3. Tertiary prevention:

  Diabetes is major cause of disability through its complications, e.g., blindness, kidney failure, coronary thrombosis, gangrene of the lower extremities, etc. The main objective at the  tertiary  level is to organize  specialized  clinics  ( Diabetes  clinics)  and units  capable  of providing  diagnostic and  management  skills of a  high order. 





 




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