Diabetes Mellitus

September 6, 2021


Diabetes Mellitus (DM) is a group of metabolic disorders characterized by chronic hyperglycemia due to impaired insulin secretion, variable degrees of peripheral insulin resistance or both.

Diabetes Mellitus is common and according to WHO approximately a 415 million adults have diabetes worldwide. This is estimated to be 1 in 11 of the world’s adult population. Diabetes is usually irreversible but patients can live a reasonably normal life by controlling blood glucose levels by lifestyle modification, exercise, and medicines and minimizing long- term complications. There are 2 main types of diabetes — type 1 and type 2, which can be distinguished by a combination of features.


Types of Diabetes

Type-1 Diabetes

Type-1 diabetes is a rare autoimmune disorder (less than 10 % of all diabetes cases). Patients are lean, younger (less than 40, average at around age 5-7 or at puberty), and are most common in Europe. Include autoimmune and idiopathic forms. Genetic susceptibility and viral factors play a role in causing autoimmune disorders against the beta cells of the pancreas. Beta cells destruction over months or years usually leading to absolute insulin deficiency.

The terms (juvenile or adult onset) or type of treatment (insulin dependent or independent) are not used now because of the overlap in age groups and treatments. Particularly the age of onset, duration of symptoms, and family history. Type-1 can occur at any age, while type-2 is increasingly being diagnosed in children.


Type-2 Diabetes

This disorder is relatively common in all populations. Over 90% of adults with diabetes have type-2 diabetes. The disease may be present for years in a subclinical form before diagnosis and the incidence increases markedly with age (greater than 50 years) and degree of obesity. Genetics play a role but there is no evidence of immune involvement. It may range from predominantly insulin resistance with relative insulin deficiency to a predominantly insulin secretory defect with insulin resistance. Insulin levels often high, especially early in the disease, may fall during the later course of the disease, further exacerbating glucose levels. Obesity and weight gain are important determinants of insulin resistance in type-2 diabetes.

Gestational Diabetes

Pregnancy causes insulin resistance in all women, but only few develop diabetes called gestational diabetes. Increase glucose level is treated with diet and medicines and insulin if needed. Glucose levels comes to normal in majority after the delivery.


Other specific forms of diabetes

Diabetes may be secondary to other conditions. These accounts for small proportion of cases. It may be precipitated by an underlying illness and may be associated with autoimmune disease or hyperlipidemia. Other causes are:

  • Genetic defects of beta-cell function,  e.g. maturity-onset diabetes of youth (MODY), Mitochondrial DNA mutations, Neonatal diabetes. Mutation in proinsulin or insulin conversion.
  • Genetic defect of insulin action: Insulin receptor mutations ( including type A insulin resistance, Leprechaunism, Rabson-Mendenhall syndrome) Acanthosis nigricans, lipodystrophies
  • Diseases of exocrine pancreas (eg, trauma, Cystic Fibrosis, Chronic pancreatitis, Tropical diabetes, Hemochromatosis, Pancreatectomy, Neoplasia.
  • Endocrinopathies eg, Cushing’s syndrome, acromegaly, Hyperthyroidism, Somatostatinoma, Aldosteronoma, Pheochromocytoma, Glucagonoma. Autoimmune polyglandular syndrome 1and 2, others
  • Uncommon forms of immune-mediated diabetes: stiff- person syndrome, Anti- insulin receptor anti bodies, others
  • Drug or chemicals : Vacor, pentamidine, Glucocorticoids, Thyroid hormone, Beta adrenergic agonist ,diazoxide, Phenytoin, Thiazide Diuretics, Protease Inhibitors, gamma interferon and therapeutic doses of niacin. Clozapine, Antiretroviral treatment (HIV)
  • Toxins eg, the rodenticide pyriminyl
  • Infections : Congenital rubella, cytomegalovirus, Coxsackie.
  • Associated with genetic syndromes e.g. Down Syndrome, Klinefelters Syndrome, Turner Syndrome, Myotonic Dystrophy, Friedreich’s Ataxia, Wolfram’s Syndrome, Huntington ‘s Chorea, Lawrence-Moon-Biedl syndrome, Prader- Willi syndrome, others.

Signs and Symptoms of Diabetes

  • Increased frequency of urine especially at night times.
  • Increased thirst and a dry mouth
  • Increased hunger, especially a predilection for sweet food.
  • Weight loss
  • Fatigue
  • Weakness
  • Mood changes and irritability.
  • Difficulty in concentration.
  • Headaches
  • Blurred vision
  • Frequent infections and poor wound healing
  • Numbness of hands and feet
  • Itchy dry skin

In early type-2 DM, symptoms may be more subtle and consist of fatigue, poor wound healing, and paresthesia. The lack of symptoms is the main reason for the delayed diagnosis of type-2 Diabetes Mellitus.

Type 2 diabetes ( T2D ) and pre-diabetes belong to a metabolic syndrome thought to be caused by resistance to insulin. Thus, people with T2D often have associated disorders including hypertension, Dyslipidemia, non-alcoholic fatty liver disease, and polycystic ovarian syndrome in women. This cluster has been termed as insulin resistance syndrome or metabolic syndrome. And is much more common in obese people.

Diagnostic Criteria

Diagnosis of diabetes is made by fasting plasma glucose level (FPG), Glycosylated hemoglobin (Hb A1c), and sometimes by oral glucose tolerance test.

The concentration of glucose measured in plasma is 11% greater than that of whole blood as red blood cells contain relatively little glucose. Venous plasma values are usually the most reliable for diagnostic purposes.


In health blood glucose is tightly regulated and maintained within a narrow range – even small deviations become important. In symptomatic patients, a single elevated blood glucose, measured by a reliable method indicates diabetes. In patients without symptoms or mildly symptomatic patients the diagnosis is confirmed by another test. Oral glucose tolerance test is done for borderline cases only.

Diagnostic Criteria Fasting Plasma Glucose
(FPG) mg /dl
Oral Glucose Tolerance Test
(OGTT) mg /dl
HbA1c %
NormalLess than 100
or < 5.6mmol/L
Less than 140
or <7.8 mmol/L
Less than 5.7
Pre diabetes100-125
or (5.6-6.9) mmol/L
or (7.8-11.0) mmol/L
Diabetes126 or more
or ≥ 7mmol/L
200 or more
or ≥ 11.1 mol/L
6.5 or more

Intermediate category or pre-diabetics are at a substantial risk for developing type-2 diabetes and cardiovascular disease in future. Type-2 diabetes is a diagnosis of exclusion. Diagnosis of type-2 diabetes is made when type- 1 diabetes and other types of diabetes are ruled out.


Risk Factors for Type 2 Diabetes Mellitus

  • Overweight BMI 25kg/m2 or more) or obesity
  • Age ≥ 45
  • First degree relative with diabetes
  • Sedentary lifestyle
  • Race, ethnicity
  • Previously identified impaired glucose test. (IFG, IGT)
  • History of gestational diabetes or delivery of baby > 4 kg (9lb.)
  • Hypertension ( BP ≥ 140/90 )
  • HDL cholesterol level ≤ 0.90 mmole/L (<35mg/dL) and/or triglycerides level ≥ 2.82 mmole/L (>250mg/dL)
  • Polycystic ovary syndrome
  • Acanthosis nigricans
  • History of cardiovascular disease

People ≥ age 45 and all adults with additional risk factors described above should be screened for DM with an  blood sugar fasting (FPG) level, HbA1C, or a 75-g  oral glucose tolerance test (OGTT ) at least once every 3 years and at least annually if results reveal impaired fasting glucose levels.


The aims are to improve symptoms of hyperglycemia and minimize the risks of long-term complications. Treatment plans for diabetes include, changes in diet, exercise, and medicines that reduce glucose levels including, insulin, oral Antihyperglycemics and other medicines to treat or prevent complications.


Education is the key in achieving and maintaining a healthy lifestyle and to manage diabetes. Diabetic patients should be well aware of the causes of diabetes, signs and symptoms, complications and self-monitoring of glucose. Insulin treated patients should be taught how to monitor their own glucose levels using finger-stick glucometers. Immediate knowledge of blood glucose can be used to guide their insulin dosing and to manage exercise and illnesses.


Blood glucose target vary according to individual but in general the pre-meal target is 90-130mg/dL and after meals less than 180 mg/dL.

Insulin is mandatory for type-1 diabetic patients but type 2 diabetes can be managed with oral glucose lowering medicines, insulin sensitizers and secretagogues in addition to insulin.

In people with type-2 diabetes, treatment of co-existing hypertension and hyperlipidemia is usually required. The target for blood pressure usually is 130/80 mmHg. Statin is advised for every type- 2 diabetic patient greater than 40 years of age irrespective of baseline cholesterol levels.

Target levels for total cholesterol is less than 150 mg/dl (or less than 4 mmole/L) and an LDL cholesterol of less than 75mg/dl (or 2 mmole/L). The same targets for type-1 diabetic patients are considered.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s