All About Type 1 Diabetes Mellitus

All About Type 1 Diabetes Mellitus


Type Diabetes Mellitus is also known as Insuin Dependent Diabetes Mellitus. It is a T-cell mediated autoimmune disease  where there is destruction of insulin-secreting β cells in the Islets of Langerhans in pancreas leading to decrease or almost no insulin production.


The pathology starts with insulinitis where Islets is infiltrated with helper cytotoxic Tcells, B lymphocytes, and activated macrophages. Only insuling secreting β cells are destroyed and other glands are intact.

Antibodies to Islets are present prior to clinical presentation of type I Diabetes and so are useful to confirm the diagnosis. The risk  is more in people ith Autoimmune thyroiditis, Coeliac disease, Addison’s Disease, pernicious anemia and vitiligo.

Genetic Association

Genetic factors count for 1/3rd of the susceptibility to type I DM. And mainly people with HLA DR3 and/or HLA DR4 are more susceptible. These tend to be tranmitted to other alleles of HLA-DQA1 and HLA-DQB1 and as these code for surface protein of cells which present as foreign and antigen to T lymphocytes, these are main determinants of gnetic susceptibility.

In first degree relatives

Identical twins have 35% of chances to have type I DM and non-identical twins have 20% of chances. Similarly HLA-identical siblings have 16% of chance and non-HLA-identical siblings have only 3% of chances. If father has this condition, children have 9% of chance to have the condition and if mother has it, Children will have 3%, and if both parents have it, there is 30% of chances that children will have it too.

Environmental predispostion

Although seasonal and geographic variations suggest that environmental factors have important role, how do they impact is uncertain. They may be directly toxic to β cells or initiating autoimmune response to the β cells. Factors are catagorised as Viruses, Drugs or chemicals or dietary constituents.


Viruses that implicate type I DM are Coxsackie virus, mumps, rubella, Cytomegalovirus, retrovirus and Epstein-Barr virus.

Dietary variants

If any child is fed with bovine milk in early infancy they are at higher risk to develop type I DM than those who are breastfed. Hypothesis are made that if exposure to microorgnisms are reduced in early chilhood, immune system doesnt develop well and it increase susceptibility to develop DM.

Signs and Symptoms of Type I DM

Clinical presentation of type I DM occur only after 80-90% of Islets are destroyed. Individual presents with following sypmtoms and signs:-

  1. Polyuria (increased urination)
  2. Polydypsia(increased thirst)
  3. Polyphagia (increased appetite)
  4. Unexplained weightloss
  5. Nocturia
  6. Fatigue

These individual have increase risk of develpoing urinary tract infectios, genital infections, hypotension and tachycardia.

Some people also resent with Diabetic Ketoacidosis which is life threatening.


Type I DM occur at younger age below 25, more in  male. Complications are also more common in male. It is more prevalent in non-hispanix whites followed by African Americans and uncommon among Asians. In USA, it has be analysed that 1 million people are diagnosed with the condition, age below 10 and incidence is increasing.


1. Urine test:-

  1. Glucose:- Presence of glucose in urine (gylcosuria) always makes it necessary to do further investigations. It is a very common investigation done in hospitals.
  2. Ketones:- Ketonuria may be present in normal individual who have been fasting of doing strenous exercise, but if it is associated with glycosuria, diagnosis becomes stronger.
  3. Protien:- Microalbuminuria or proteinuria in absence of of urinary ract infection indicates diabetic nephropathy and or increased risk of macrovascular disease.

2. Blood test:-

  1. Glucose:- Blood fr glucose test may be affected if the person has eaten his/her meal. Thankfully there are normal values set for both random blood sugar as well as fasting blood sugar. Easiest and cheap method. A test called Oral Glucose Tolerance Test (OGTT) is performed.
  2. Glycated Hemoglobin (HbA1C) :- It provides the exact measure of glycemic control of last 3 months. Yet it may be unreliable in anemia or during pregnancy and difficult to assay in patients with uremia and hemoglobinopathy.



Aims of management is to improve the sypmtoms of hyperglycemia and minimise the risks if long term microvasuclar and macrovascular complications. Management includes following things:-

1. Lifestyle modification

People who lead sedentary lifestyle must start doing regular exercise. They also should start eating healthy, better to consult a dietician. Avoiding alcohol consumption and smoking is must.

2. Weight management:-

Reducing weight is important for obese people by reducing the amount to calorie and increasing energy expenditure. It has positive effect in HbA1C.

3. Insulin Therapy:-

Insulin is injected subcutaneously several times a day, around umblicus, anterolateral surface of thigh, upper arms and buttocks. Dose depends upon the sugar level of the patient. There are various insulin preparations according to their duration of action.

  1. Rapid-acting (Insulin analogues: lispro, aspart, glulisine) :- 3 to 4.5 hours pf action
  2. Short-acting (Soluble (regular)):- 4 to 8 hours of action
  3. Intermediate-acting (Isophane,lente):- 7 to 14 hours of action
  4. Long-acting (bovine ultralente):-12 to 30 hours of action
  5. Long-acting(Glargine, detemir):- 18 to 24 hours of action


Type I DM is known for high morbidity and early age mortality. About 60% percent of patient with this diabetes donot develop complication for long term. Most of them face mortality due to Cardiovascular diseaseand end stage renal disease. Following are the complication of diabetes mellitus in general.



1.       Diabetic Retinopathy:- Impaired Vision

2.       Diabetic Nephrpathy:- Renal Failure

3.       Peripheral Neuropathy:- Sensory loss, Pain and motor weakness

4.       Autonomic Neuropathy:- Postural hypotension, gastopathies

5.       Diabetic Foot/ulcer



1.       Mayocaridal Infarction

2.       Transient Ischaemic attack or Stroke

3.       Claudication and Ischemia

Maintaing healthy lifestyle and weight, keeping up with treament will delay the onset of complicaion and may lengthen the lifespan. Awareness regarding this condition and training the expertise is also helpful.





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