Diabetes Mellitus (DM)
The term diabetes mellitus encompasses the abnormalities in carbohydrate metabolism that result in hyperglycemia. Insulin, the hormone that effects sugar entering the cells, can be absent or its production can be impaired (TYPE 1) or there can be “insulin resistance” of tissues to insulin (TYPE 2).
The prevalence of DM in the U.S. is >8%, and it consumes more healthcare resources than any other illness. Treatment requires continuous management of alterations in blood sugar by keeping the blood sugar within a desired range that extends life expectancy and reduces its complications.
The mainstay of managing diabetes is the administration of insulin. Other less invasive methods can be used prior to insulin becoming necessary which include oral hypoglycemics and diet modification.
The Types of Diabetes
Type 1 DM is an autoimmune disease in which the insulin-producing cells in the pancreas are destroyed. It makes up about 5-10% of the cases of DM. It begins in childhood in 3/4 of the cases, creating complications beginning earlier than those seen in Type 2 DM.
Type 2 DM is a decrease in sensitivity to insulin, which is called a “relative” insulin deficiency. It makes up 90% of the cases of DM. The risk of developing it rises with age and its prevalence continues to rise as more people are living longer. Because of its “relative” insulin deficiency, as opposed to the “absolute” deficiency of Type 1 DM, initial treatment can involve oral hypoglycemics that lessen this resistance.
In diabetes, co-morbidities impact each other negatively. High lipids, especially triglycerides, low HDL-cholesterol, hypertension, obesity, and other characteristics collectively called “the metabolic syndrome” combine with diabetes to cause worsening of all of them. The metabolic syndrome is an important consideration because of the increased risk it creates toward developing Type 1 DM.
In diabetes, the narrow range of acceptable blood sugars requires aggressive management to prevent complications. These include diabetic retinopathy, nephropathy, diabetic ulceration and foot pain, and cardiovascular complications.
How Is Diabetes Mellitus Diagnosed?
The Metabolic Syndrome
The metabolic syndrome is a cluster of findings that taken together make it a risk factor for developing Type 2 diabetes. The abdominal obesity of the metabolic syndrome is associated with insulin resistance that results in subsequent hyperglycemia and vascular disease. The elevated triglycerides, low HDL-cholesterol, hypertension, and elevated fasting plasma glucose that are seen with this syndrome interrelate in negative ways.
The diagnosis of DM is via documentation of hyperglycemia. Any one of the three American Diabetes Association criteria below establishes the diagnoses of diabetes:
- Fasting plasma glucose (FPG) values ≥126 mg/dL. (Normal is < 100.)
- Two-hour plasma glucose values of ≥200 mg/dL after a 75 g oral glucose challenge in the oral glucose tolerance test (OGTT). (Normal is < 140.)
- A1c values ≥6.5%. (Normal is 6%.) The glycated hemoglobin A1c is a reflects a composite of glycemic control over the previous month(s).
Any abnormal result of these criteria require re-testing.
Other Causes of Hyperglycemia
There are other causes of hyperglycemia that must be ruled out. They include “stress hyperglycemia,” which is not DM but is a risk for developing it. Steroids and other medications during severe illness can cause stress hyperglycemia.
Diabetes occurs with and augments other co-morbidities. The work-up for diabetes includes seeking and identifying co-morbidities to implement a global treatment plan. These include the following:
- Smoking cessation
- Hypertension, hyperlipidemia, and other cardiovascular risks
- Visual changes due to diabetic retinopathy and hearing impairment
- Kidney function tests, liver abnormalities, and periodontal disease
- Cognitive impairment
- Bone weakness/fractures
Management of Diabetes Mellitus
In any illness, management and treatment is based on risk vs. benefit and consideration of the least invasive means. Since lowering blood sugar is done by methods ranging from lifestyle alterations to injecting insulin, a personalized regimen is necessary for each diabetic patient. Within this range, from least invasive to most invasive, are the oral hypoglycemics, such as metformin.
Type 2 DM
The treatment goal in Type 2 DM is a drop in glycated hemoglobin A1c to ≤7%. Every 1% drop lowers the complication rate due to vascular injury.
- Education and life-style alterations: Patients who are knowledgeable of their condition are more compliant with treatment and do better. Counseling on nutrition and weight reduction through caloric restriction, physical exercise, and preventing complications go hand-in-hand with pharmacologic therapy.
- Medication should begin at the time of diagnosis: Metformin is an oral hypoglycemic that is the recommended initial medication. It decreases liver production and intestinal absorption of glucose and improves insulin sensitivity. There are other oral hypoglycemics, but metformin has been associated with fewer episodes of hypoglycemia–a risk of any sugar-lowering strategy. Persistent hyperglycemia in spite of lifestyle alterations and oral hypoglycemics indicates the need for insulin administration.
Type 1 DM
Type 1 DM requires insulin, which is injected. The treatment goal in Type 1 DM is a glycated hemoglobin A1c of 7%. Insulin is given daily for a baseline level and supplemented when necessary by pre-meal boluses of shorter-acting insulin. Other methods, such as continuous infusion by a pump, add to the treatment choices.
For Type 2 DM, biannual A1c levels are obtained in patients with a history of good glycemic control. This is prescribed more frequently in those adjusting to new medications or doses or those who have not met their therapeutic goals. With good glycemic control, the lifestyle changes and metformin monotherapy protocol can continue indefinitely. For those who fail to reach goals, a combination with insulin is required.
For Type 1 DM, self-monitoring of blood glucose is an important part of diabetes therapy, and a combination of glucose measurements by physician and self-testing by patient has been proven to be the best surveillance method.
Prevention of Type 1 Diabetes Mellitus
Type 1 DM results from the destruction of the insulin-producing pancreatic islet cells due to autoimmune disease. Identification of Type 1 DM cannot occur until the signs and symptoms of DM occur, by which time most of the islet cells have already been destroyed. Immunosuppressive or anti-inflammatory therapy for Type 1 DM is still in the research stage. With destruction of islet cells underway, Type 1 DM is difficult to slow down. The experimental nature of autoimmune therapy and the difficulty in pinpointing the onset of the illness makes prevention unfeasible. The genetic basis for Type 1 DM makes watchful waiting the only strategy for those at risk.
Prevention of Type 2 Diabetes Mellitus
Identifying those at risk is the first step of preventing Type 2 DM. Identifying susceptible individuals is by determining the hemoglobin A1c or fasting plasma glucose annually in persons >45 years of age who have a BMI>25 kg/m2 and who have one or more additional risk factors for diabetes:
- Abnormal glucose metabolism (fasting plasma glucose 100-125 mg/dL, 2-hour OGTT result >140, or A1c 5.7 -o 6.4 %).
- Family history of diabetes mellitus in a first-degree relative
- Sedentary lifestyle
- History of gestational diabetes (women)
- Dyslipidemia (high triglycerides, low HDL-cholesterol, elevated LDL-cholesterol)
The metabolic syndrome encompasses these risk factors.
Prevention via lifestyle modification includes exercise, weight loss, a healthy diet, and smoking cessation. The benefits of lifestyle modification persist for three years or more for those with “pre-diabetes” (the elevations cited above for glucose, OGTT, and A1c levels).
Oral hypoglycemics are used in those at risk, with metformin (850 mg. twice daily) added in conjunction with the lifestyle changes.