Diabetes Mellitus

What is Diabetes Mellitus

Diabetes mellitus (DM) is a chronic disorder of carbohydrate, protein, and fat metabolism in which there is a discrepancy between the amount of insulin required by the body and the amount of insulin available. DM affects over 10 million persons in the United States, and more than 35,000 people die from it each year. DM is classified into several categories.
The beta cells of the pancreas produce insulin and a protein called C-peptide, which are stored in the secretory granules of the beta cells and are released into the bloodstream as blood glucose levels increase. Insulin transports glucose and amino acids across the membranes of many body cells, particularly muscle and fat cells. It also increases the liver storage of glycogen, the chief carbohydrate storage material, and aids in the metabolism of triglycerides, nucleic acids, and proteins.
Long-term complications such as disease of the large and small blood vessels lead to cardiovascular disease (coronary artery disease, peripheral vascular disease, hypertension), retinopathy, and renal failure. Diabetic patients also have nerve damage (neuropathy) that can affect the peripheral nerves, resulting in numbness and pain of the hands or feet. Because diabetic patients are hyperglycemic, they are at higher risk for infection because an elevated glucose encourages bacterial growth. The combination of peripheral neuropathies with numbness of the extremities, peripheral vascular disease leading to poor tissue perfusion, and the risk for infection makes the diabetic patient prone to feet and leg ulcers.

Causes Of Diabetes Mellitus
The cause of Diabetes Mellitus is not known, but genetic, autoimmune, viral, environmental, and socioeconomic factors have all been implicated in the development of the disease. Type 1 Diabetes Mellitus is most likely an autoimmune response in patients with genetic susceptibility. Following an environmental stimulus such as a virus or bacteria, antibodies attack the beta cells of the pancreas and cause insulitis Inflammation and destruction of the beta cells. It is thought that type 2 Diabetes Mellitus is caused by hereditary insulin resistance or abnormal insulin production. If insulin resistance is acquired rather than inherited, it is usually the result of obesity.

GENETIC CONSIDERATIONS
Diabetes Mellitus is a complex disorder, with several genes and environment working together. Type 1 is an autoimmune disease with about a 40% to 50% twin concordance rate in monozygotic twins. It has been linked to the HLA allele (DR3, DR4) which accounts for more than 50% of cases, but there have been links to other loci as well. Type 2 is a heterogeneous disease with varied genetic linkage in different populations. In Mexican Americans, loci on chromosomes 2 and 11 have been linked; in Finns, a locus on chromosome 12, while in the Pima Indians another locus on chromosome 7 is implicated. Monozygotic twins show 50% to 100% concordance after age 45. Fifty percent of those affected have an affected parent. Genes associated with DMT2 include Calpain-10 (ch 2)-protease, PPAR 8, and mutations in mitochondrial DNA. Single gene disorders of the beta cell can also cause familial Diabetes Mellitus.

Types of Diabetes Mellitus

Diabetes Mellitus TYPE 1
Patients are dependent on insulin for prevention of hyperglycemia or ketosis. Referred to as insulin-dependent diabetes mellitus (IDDM). Approximately 10%–20% of patients with Diabetes Mellitus have this type. The most serious life-threatening problem is diabetic ketoacidosis. Time of onset is usually under age 20 years. Beta cells of pancreas have insulitis (pancreatic inflammatory response) with beta cell destruction

Diabetes Mellitus TYPE 2
Patients are not dependent on insulin. Patients have either insulin resistance or impaired insulin secretion. Referred to as non–insulin-dependent diabetes mellitus (NIDDM). Most common type of Diabetes Mellitus: approximately 80%–90% of Diabetes Mellitus patients have this type. The most serious problem is the development of hyperosmolar hyperglycemic nonketotic syndrome (HHNS). Time of onset is usually over age 30 years. Beta cells have no insulitis; resistance to insulin occurs as the target cells.

Gestational diabetes mellitus (GDM)
Patients develop glucose intolerance during pregnancy

Other types of Diabetes Mellitus
Diabetes develops secondary to other conditions, including pancreatic, hormonal, or endocrine disease and insulin resistance; or it is drug-induced

Malnutrition related Diabetes Mellitus
Occurs in underdeveloped countries to individuals with a history of malnutrition

GENDER, ETHNIC/RACIAL, AND LIFE SPAN CONSIDERATIONS
Although Diabetes Mellitus can occur at any time and in both genders, the incidence increases with age, most commonly occurring in adults after age 30. Type 1 most commonly develops in childhood before age 20 but can occur at any age. Onset is often very abrupt. Because of the early age of onset, teenagers often deal with the long-term complications of the disease. Whites are more typicallyaffected with type 1 DM than are people of color. Type 2 Diabetes Mellitus usually occurs after the age of 30, particularly in individuals who are overweight or have hereditary factors. Gestational diabetes mellitus (GDM), which is present during pregnancy, occurs in 3% of pregnant women, usually in those older than 30. Type 2 Diabetes Mellitus is more common in Native Americans, Hispanics, and African Americans than in whites but the incidence is equal in females and males in all populations. Type 2 Diabetes Mellitus is becoming increasingly common because Diabetes Mellitus prevalence increases with age, and people are living longer than in past centuries. In addition, it is also more frequent in younger people in accordance with the rising prevalence of childhood obesity.

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