Type 2 Diabetes Mellitus

Type 2 diabetes mellitus, type 2 diabetes, or just diabetes is a common and increasingly prevalent disease characterized by high blood sugar (hyperglycemia) and resistance to the effects of insulin. Diabetes is the most common disease of the endocrine system and one of the most commonly-encountered diseases in adult medicine; its high prevalence is due in part to the abundance of "cheap calories" and consequent obesity in the developed world.

The impact of diabetes is difficult to overstate. In the US, about 24 million people have the disease, about 6 million of whom are undiagnosed and not receiving treatment. In 2007, the disease contributed to or caused the death of over 284,000 Americans, and resulted in economic damages (lost or decreased productivity, direct costs associated with treating the disease or its complications, etc.) of about $174 billion^[1] Improved understanding of the causes and complications of type 2 diabetes continues to provide better options for preventing and managing the disease.

Other Names

• Diabetes, without further specific terms (as discussed below)
• Older names no longer used: ^[2]
  • Adult-onset diabetes is discouraged because children and adolescents are also at risk for the disease
  • Type II diabetes, using the Roman numeral is discouraged due to possible confusion with the Arabic number 11
  • Noninsulin-dependent diabetes (NIDDM) is discouraged because type 2 diabetics sometimes use insulin

When used alone, diabetes refers to diabetes mellitus (as opposed to diabetes insipidus). Because over 90% of diabetics have type 2 diabetes (as opposed to type 1 diabetes), diabetes is often used to refer specifically to type 2 diabetes mellitus.

Introduction

Type 2 diabetes occurs when not enough insulin is produced by the body for it to function properly, or when the body’s cells do not react to insulin. This is called insulin resistance. Type 2 diabetes is far more common than type 1 diabetes, which occurs when the body does not produce any insulin at all. Around 95% of all people with diabetes have type 2 diabetes. If you have type 2 diabetes, you may be able to control your symptoms simply by eating a healthy diet, and monitoring your blood glucose level. However, as type 2 diabetes is a progressive condition, you may eventually need to take insulin medication, usually in the form of injections. Type 2 diabetes is often associated with obesity.Obesity-related diabetes is sometimes referred to as maturity onset diabetes because it is more common in older people

From NIOSH (Part 1 of 3)


From NIOSH (Part 2 of 3)


From NIOSH (Part 3 of 3)

Causes

Insulin is a hormone that is needed to control the amount of glucose (sugar) in your blood. Normally, the amount of sugar in the blood is controlled by a hormone called insulin, which is produced by the pancreas (a gland that is located behind the stomach).

When food is digested and enters the bloodstream, insulin helps to move any glucose out of the blood and into cells, where it is broken down to produce energy. However, in diabetes, because there is either not enough insulin, or because there is a poor response (resistance) to insulin, the body is unable to fully use the glucose in the blood stream.

If you have type 2 diabetes, there is either not enough insulin to move glucose out of your bloodstream, or the insulin that is there is ineffective in moving glucose. It is also possible to have type 2 diabetes as a result of both of these reasons.

Type 2 diabetes is caused by a combination of genetic and environmental factors. Many genes have been implicated in causing or increasing the likelihood of the disease.^[3] The disease is also strongly associated with environmental factors that contribute to low energy expenditure and obesity; the risk of diabetes increases dramatically with body mass index (BMI, a measure of obesity based on height and weight).^[4]

Signs and Symptoms

The classically-recognized signs and symptoms of diabetes are excessive thirst and urination (polydipsia and polyuria, respectively) and excessive hunger (polyphagia), all of which are attributable to abnormal carbohydrate metabolism.

In contrast to type 1 diabetes, which is fatal if left untreated, people who meet the diagnostic criteria for type 2 diabetes can live with the disease for years without a formal diagnosis (and without receiving the benefits of treatment). As a result, people with undiagnosed diabetes often come to medical attention with preventable complications of the disease such as neuropathy (noticed as problems with sensation), retinopathy (manifested as blurry vision), sores that may be slow to heal, or problems attributable to cardiovascular disease.

Diagnosis

Main Article: Diagnosis of Diabetes

Diagnosis of Diabetes can be based on any of three criteria. In the absence of unequivocal hyperglycemia, each test must be repeated on a subsequent day. The three criteria^[5] are:

• Symptoms of diabetes (excessive thirst, excessive urination, and unexplained weight loss) together with a plasma glucose value of 200 mg/dL or greater
• Plasma glucose of 126 mg/dL or higher after an overnight fast on more than one occasion
• Plasma glucose of 200 mg/dL or higher obtained two hours after drinking a solution with 76 g of glucose

Hemoglobin A1C is not a recommended diagnostic test, although it forms an important part of monitoring the long-term blood glucose control in people who are known to have the disease.

Exams and Tests

Blood glucose testing is the most important way to monitor the adequacy of treatment; however, since much of the morbidity and mortality associated with diabetes comes from cardiovascular disease (CVD), exams and tests for CVD also form an integral part of the overall diabetes treatment plan. CVD risk factors are described separately.

To determine the adequacy of blood glucose control, frequent self-testing is recommended with blood samples obtained from a fingertip and analyzed on a small blood glucose meter. Recommendations for time and frequency vary between individuals, and health care providers often note that patients are reluctant to test their own blood sugars because of the associated pain, expense, and inconvenience.^[6]

Another way to assess the adequacy of blood glucose control is by measuring glycosylated hemoglobin, or HbA1C. This is a form of hemoglobin that has become irreversibly attached to glucose. Normally, only about 5% of a person's hemoglobin is decorated with sugar molecules in this way. Since the rate of attachment is proportional to the blood glucose concentration, the HbA1C result accurately reflects blood glucose values over the previous several weeks to several months.

Urine testing for sugar is based on the observation that at very high blood glucose concentrations, sugar is lost in the urine(glycosuria). The test is no longer widely used, in part because of the wide availability of blood glucose monitors and in part because it does not reflect changes in blood glucose in the normal or below-normal range.

Prevention

Main Article: Steps to Lower Your Risk of Getting Diabetes

Several interventions have been shown to delay or reduce the risk of transitioning from prediabetes to outright diabetes. Intensive efforts to modify the diet and exercise patterns of people at risk for diabetes, for example, reduce the incidence of disease by 58%, and treatment of prediabetes with drugs used to treat diabetes reduces the risk of transitioning to diabetes by 25% to 49%.^[7]

Related Videos

In this video from BigThink, David L. Katz MD MPH, Director of Yale University’s Prevention Research Center, discusses how to put the findings of the Diabetes Prevention Program to work in every town in America:

Dr. Katz also describes how the gap between knowledge and action belies the notion that knowledge is power, when it comes to preventing chronic disease (particularly Type 2 Diabetes and heart disease):

Treatment

Main Article: Treatments for Type 2 Diabetes

The American Diabetes Association has published a document "Standards of Medical Care in Diabetes" that describes recommendations for screening, diagnosing, and caring for people with diabetes.^[8] A similar document is published by the American Association of Clinical Endocrinologists.^[9]

There are several classes of drugs for use in type 2 diabetes:

• Sulfonylureas stimulate the pancreas to make more insulin.
• Biguanides, exemplified by metformin, decrease the amount of glucose made by the liver.
• Alpha-glucosidase inhibitors slow the absorption of the starches eaten.
• Thiazolidinediones , for example, pioglitazone, increase the patient's sensivity to insulin.
• Meglitinides, like the sulfonylureas, stimulate the pancreas to make more insulin.
• D-phenylalanine derivatives help the pancreas make more insulin quickly.
• Combination oral medicines put together different kinds of pills to enhance the effectiveness.
• Insulin Therapy is only available through injections. It reliably decreases blood glucose but increases the risk of weight gain and symptomatic low blood sugar episodes.

A typical approach to treatment starts conservatively, with recommendations for increased physical activity and weight loss. If blood sugar values remain high, pharmacological options start with monotherapy (with a single drug), typically metformin. If blood glucose control remains inadequate (as determined by HbA1C), additional drugs are added to the treatment regimen. Insulin is usually added to the treatment regimen after a combination of three oral drugs has been tried. Comprehensive therapy requires a multifaceted approach to the treatment of high blood sugar, dyslipidemia, control of weight and blood pressure, and the associated comorbidities of diabetes.

Diabetes Self-Management

Main Article: Managing Diabetes

If you have type 2 diabetes, you will need to look after your health very carefully. Ensuring that you lead a healthy lifestyle by eating a healthy, balanced diet, exercising regularly and looking after your condition can, in many cases, be enough to control your blood glucose levels without the need for further treatment.

Caring for your health will also make treating your diabetes easier and minimize your risk of developing any complications.

Your GP and diabetes care team will be able to advise you about what you need to do to ensure that you remain healthy and reduce your risk of developing further problems. They may also refer you to other specialists within your care team, such as a dietitian, for further advice and support.

Some of the advice that you will receive in order to treat your condition is outlined on the Managing Diabetes article.

Reversal of type 2 diabetes

Intensive insulin treatment with a goal of normoglycaemia can cause early diabetes to remit in about 25% of patients after one year of follow-up.^[10]

In some patients with diabetes who are dramatically overweight, bariatric surgery (i.e., surgery that modifies the stomach and/or intestines to restrict food intake) has been shown to reverse type 2 diabetes entirely.^[11]

History/Etymology

The word "diabetes" is taken from the Greek word for siphon, a combination of the prefix dia- (meaning through) and bainen meaning to go. The word refers to excessive urine production and was coined as a name for the disease by Demetrios of Apamaia in 200 BC. The word mellitus was added in 1675 by Thomas Willis is taken from the Greek word mel (referring to the sweetness of honey) to describe the sweet taste of diabetics' urine.

The earliest records of diabetes mellitus are at least 3000 years old.^[12] Most descriptions are of the severe disease in children leading to profound thirst, wasting, and death, the disease now known as type 1 diabetes.

Epidemiology

Diabetes is rapidly increasing in the developed world, and there is some evidence that this pattern will be followed in much of the rest of the world in coming years. The CDC has characterized the increase as an epidemic. In addition, whereas this disease used to be also seen primarily in adults over age 40, in contrast to type 1 diabetes, it is now increasingly seen in children and adolescents, an increase thought to be linked to rising rates of obesity in this age group, although it remains a minority of cases. The disease continues to be underdiagnosed, meaning that many people who have the disease and would benefit from treatment are at incresed risk for (preventable) long-term complications. ^[13]

External Links

• Diabetes Teaching Center at the University of California, San Francisco

References

1. ↑ Diabetes Research Institute, 2007. Diabetes Fact Sheet
2. ↑ Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 25:S5-S20, 2002. full text
3. ↑ Freeman H, Cox RD. Type-2 diabetes: a cocktail of genetic discovery. Hum Mol Genet. 2006 Oct 15;15 Spec No 2:R202-9. Abstract | Full Text | PDF
4. ↑ Hamilton MT, Hamilton DG, Zderic TW. Role of low energy expenditure and sitting in obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease. Diabetes. 2007 Nov;56(11):2655-67. Abstract | Full Text | PDF
5. ↑ American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes Care. 2006 Jan;29 Suppl 1:S43-8. Citation | [Full Text | PDF
6. ↑ Arnold-Wörner N, Holle R, Rathmann W, Mielck A. The importance of specialist treatment, treatment satisfaction and diabetes education for the compliance of subjects with type 2 diabetes - results from a population-based survey. Exp Clin Endocrinol Diabetes. 2008 Feb;116(2):123-8. Abstract
7. ↑ Irons BK, Mazzolini TA, Greene RS. Delaying the onset of type 2 diabetes mellitus in patients with prediabetes. Pharmacotherapy. 2004 Mar;24(3):362-71. Abstract
8. ↑ American Diabetes Association. Standards of medical care in diabetes--2008. Diabetes Care. 2008 Jan;31 Suppl 1:S12-54. Citation | Full Text | PDF
9. ↑ AACE Diabetes Mellitus Clinical Practice Guidelines Task Force. American Association of Clinical Endocrinologists medical guidelines for clinical practice for the management of diabetes mellitus. Endocr Pract. 2007 May-Jun;13 Suppl 1:1-68. Citation
10. ↑ Weng, Jianping et. al. "Effect of intensive insulin therapy on beta-cell function and glycaemic control in patients with newly diagnosed type 2 diabetes: a multicentre randomised parallel-group trial." Lancet 371 (2008): 1753-60 - Abstract
11. ↑ Buchwald H, Avidor Y, Braunwald E, et al. Bariatric surgery: a systematic review and meta-analysis. JAMA. 2004 Oct 13;292(14):1724-37. Abstract | Full text | PDF
12. ↑ Schadewalt H. The history of diabetes. In: Diabetes, its medical and cultural history : outlines, texts, bibliography ; edited by Dietrich von Engelhardt. New York: Springer-Verlag, 1989
13. ↑ Ollerton RL, Playle R, Luzio SD, Owens DR. Underdiagnosis of type 2 diabetes by use of American Diabetes Association criteria. Diabetes Care. 1999 Apr;22(4):649-50. Abstract | PDF