The Two Types of Diabetes Mellitus
Elevated Glucose Due to Pancreatic Dysfunction or Insulin Resistance
Sep 27, 2008
Diabetes mellitus (DM) is a condition of abnormal carbohydrate metabolism. When one hears about DM, it is often referred to by its most common categories: type 1 and type 2. These types are similar in their effects on the body but differ in their mechanisms of action and modes of treatment.
Pathophysiology
In a nondiabetic individual, the pancreas secretes insulin from its beta cells in response to an increase in blood sugar following a meal. This endocrine hormone has multiple actions, such as stimulating cells to take glucose from the blood and inhibiting the liver from producing its own glucose. These actions have the net effect of keeping blood glucose under control.
DM is characterized by a persistent elevation in blood glucose (hyperglycemia). Specifically, DM type 1 is an autoimmune disease whereby the pancreas is attacked by the immune system, resulting in deficient insulin production. In contrast, DM type 2 is caused by cellular resistance to insulin, often seen with obesity, but this may ultimately lead to decreased production of insulin by the pancreas.
Symptoms and Signs
Patients with uncontrolled diabetes mellitus may urinate excessively (polyuria) and become thirsty because the glucose filtered into the kidneys has the tendency to pull water with it. They may experience increased appetite and weight loss; the absence of functioning insulin prevents cells from obtaining the carbohydrates they need and allows muscle and fat to break down. Muscle cramping and fatigue may also occur.
DM also has long-term effects. Uncontrolled elevations in blood glucose can damage the retina of the eye (retinopathy), cells and tissues in the kidneys (nephropathy), peripheral nerves (neuropathy), and small arteries (vasculopathy). For neuropathy and vasculopathy, a susceptible but overlooked anatomical location for these problems is the foot, because a diabetic patient cannot sense any forces damaging the foot and deliver blood quickly for wound healing. In fact, DM is a major cause of blindness, kidney failure, and lower extremity amputations and a major risk factor for atherosclerosis.
Diagnosis
For patients with symptoms of excess urination, thirst, appetite, and weight loss, DM is diagnosed when a random blood glucose level is found to be at least 200 mg/dL. If the patient is asymptomatic, DM is diagnosed when a blood glucose level taken after a fasting period is at least 126 mg/dL on two different occasions. For DM type 2, another type of glucose test involves the oral administration of 75 grams of glucose followed by a blood glucose level check two hours later.
Other laboratory tests can be done to evaluate DM. For example, the presence of urine microalbumin indicates abnormal leakage of protein through the kidneys. If DM is a long-standing condition, the hemoglobin A1c test can assess severity of DM. This measures the amount of hemoglobin in red blood cells that has glucose bound to it.
Treatment
The treatment for DM depends on the type of DM involved. DM type 1 requires injection of insulin via hypodermic needles or continuous insulin infusion pumps whereas DM type 2 is treated with one or more of the following medications:
- Sulfonylureas (glyburide, glipizide, and glimepiride) to stimulate release of insulin from pancreatic cells
- Biguanides (metformin) to decrease glucose production by the liver
- Thiazolidinediones (rosiglitazone and pioglitazone) to increase glucose uptake by cells
- Insulin to correct deficient insulin production when hyperglycemia persists despite the above oral medications
Besides correcting the blood glucose level, patients must monitor their diet and activity levels so that their treatment regimen corrects hyperglycemia without causing hypoglycemia. Treatment must also address any of the complications of DM, including but not limited to dehydration, kidney disease, heart attack, and stroke.
