Types of Diabetes Mellitus

Nearly 23.6 million Americans (approximately 8% of the population) have diabetes mellitus, and millions more have diabetes and do not know it. The cost of treating diabetes in the United States is approximately $132 billion a year (Luger & Chabanuk, 2009).

Latent autoimmune diabetes (LADA) is a type 1 diabetes, according to the World Health Organization. Other names for this condition are “slow onset type 1 diabetes” or “type 1.5 diabetes.” It is believed that the presence of islet cell antibodies in the blood (which are not present in healthy individuals) will eventually destroy the beta cells, and insulin production will cease. Patients with LADA are usually not overweight, have no signs of metabolic syndrome, and may have a history of personal or familial autoimmune disease. The diagnosis is based on three criteria: (1) onset after age 30, (2) islet cell antibodies circulating in the blood, and (3) insulin is not required sooner than 6 months after diagnosis. Patients can be misdiagnosed as type 2 diabetes, and rapid failure of oral hypoglycemic drugs suggests LADA. Evidenced-based management suggests that metformin can be used in the early phase and insulin should be started within 1 year of diagnosis; both may offer some protective effects against the destruction of the beta cells, whereas sulfonylureas may hasten destruction of beta cells and therefore are not recommended (Kapustin, 2008).

Gestational diabetes may occur as a result of the stress of pregnancy. It may be treated with diet, oral hypoglycemia agents, or insulin. After delivery, the condition must be reevaluated; approximately 5% to 10% of women with gestational diabetes go on to be diagnosed with type 2 diabetes after delivery. The baby also carries an increased risk of type 2 diabetes later in life.

Etiology and Pathophysiology

At least four sets of factors influence the development of diabetes mellitus: genetic, metabolic, microbiological, and immunologic. In a recent study funded by the National Institutes of Health (2010) scientists used computer analysis to evaluate 226 environmental factors affecting diabetes. They found that a pesticide derivative (PCB) was strongly associated with developing diabetes, and that the nutrient beta-carotene served a protective role.

Genetic factors are included in the etiology of diabetes because diabetes tends to run in families. It is known that the risk of having some form of diabetes increases in proportion to the number of relatives who are affected, the genetic closeness of the relatives, and the severity of their disease.

Metabolic factors involved in the etiology of diabetes are many and complex. Emotional or physical stress can unmask an inherited predisposition to the disease, probably as a result of glucogenesis induced by increased production of hormones from the adrenal cortex (especially the glucocorticoids). Perhaps even more significant than metabolic factors is the association of type 2 diabetes and obesity. About 80% of type 2 diabetes patients are obese (greater than 20% above their ideal body weight), and there is a higher incidence of type 2 diabetes in persons who lead a sedentary life and eat a high-calorie diet. With weight reduction and increased physical activity, blood glucose can be restored to normal levels and maintained there—hence the importance of diet and exercise in the management of type 2 diabetes. In type 2 diabetes there also seems to be a relationship to aging and a reduction in the function of the pancreatic beta cells and how they synthesize insulin.

Signs, Symptoms, and Diagnosis

The American Diabetes Association (ADA) recommends screening all adults, especially if overweight, for type 2 diabetes starting at age 45, to be repeated every 3 years: either hemoglobin A_1c (A1C or HbA_1c), fasting plasma glucose (FPG), or 2-hour 75-g oral glucose tolerance test (OGTT) are appropriate screening methods. The ADA recommends that screening begin at an earlier age, and at more frequent intervals, if the person has one or more risk factors associated with type 2 diabetes (ADA, 2009).

Fatigue and muscular weakness occur because the glucose needed for energy is not metabolized properly. Weight loss in patients with type 1 diabetes occurs for two reasons: (1) the loss of body fluid; and (2) in the absence of sufficient insulin, the body begins to metabolize its own proteins and stored fat. The oxidation of fats is incomplete and fatty acids are converted into ketone bodies: beta-hydroxybutyric acid, acetoacetic acid, and acetone. When the kidney is unable to handle accumulated ketones in the blood, ketosis occurs. The overwhelming presence of the strong organic acids in the blood lowers the pH and leads to a severe and potentially fatal acidosis. The metabolism of body protein when insulin is not available causes an elevated blood urea nitrogen (BUN) level. This is because the nitrogen component of protein is discarded when the body metabolizes its own protein to obtain the glucose it needs.

People with diabetes are prone to infection, delayed healing, and vascular diseases. Poor control of diabetes makes the person prone to develop an infection. The propensity for infection is thought to be partly a result of decreased normal function of leukocytes and abnormal phagocyte function. Another contributing factor to infection and delayed healing probably is decreased blood supply to the tissues because of atherosclerotic changes in the blood vessels. An impaired blood supply means a deficit in the protective cells brought by the blood to a site of injury.

It is believed that the neurologic, vascular, and metabolic complications of diabetes predispose the person to infections by allowing organisms to enter tissues that are normally better defended and less accessible. For example, a neurogenic bladder predisposes the patient to stagnant urine and accumulations of bacteria, and a leg ulcer resulting from peripheral vascular disease is without the protection of the skin as a barrier to organisms.

Management of Diabetes

There is no cure for diabetes mellitus; the goal is to maintain blood glucose and lipid levels within normal limits and to control these factors to prevent complications. Studies have demonstrated that there are benefits of tight glycemic control (control of glucose in the blood) for people with both type 1 and type 2 diabetes. Patients attempting tight control follow an intensive therapy plan of blood glucose testing and insulin injections, three or more times a day, or they use an insulin pump. There are some risks associated with perfect control of blood glucose levels, and “tight control” is not indicated for every patient. The most serious control issue is hypoglycemia, or insulin reaction. In a recent study (Finfer & Delaney, 2008), tight glucose control was associated with increased mortality rate in critically ill patients. American Diabetes Association guidelines now recommend glucose targets of 140 to 180 mg/dL for critical patients. For the noncritically ill, premeal target is 140 mg/dL or less and random readings should be 180 mg/dL or less. The health care provider will adjust these parameters for the individual patient.

Research has demonstrated that lowering A1C levels to 7% is associated with decreased microvascular complications (eye, kidney, and nerve diseases) of diabetes. If the patient is elderly and very frail or if the life expectancy is short, the American Geriatrics Association recommends an A1C of 8% (Lee, 2009).

The protocol for control of diabetes mellitus is highly individualized and depends on the type of diabetes a person has, age, general state of health, ability to follow the prescribed regimen, and acceptance of responsibility for managing illness, along with a host of other factors.

The overall goal of diabetes management is achieved when fasting blood glucose stays within normal limits, A1C tests show that blood glucose has stayed within normal limits from one testing period to the next, the patient’s weight is normal, blood lipids remain within normal limits, and the patient has a sense of health and well-being.