Diabetes is a general term to describe disorders in which there is excess urine excretion. There are two types, diabetes mellitus and diabetes insipidus. Diabetes insipidus is a rare disorder in which the kidney does not properly reabsorb water due to a lack of the posterior pituitary hormone ADH, whereas diabetes mellitus is a more common disorder that is marked by elevated blood glucose (commonly referred to as blood sugar). When the term diabetes is used alone, it is referring to diabetes mellitus.
Within the cell, glucose is converted into energy and is used as the major fuel for the body. It is so important that the body has storage forms of glucose (glycogen) to call upon when needed. It can also break down muscle protein to form glucose under extreme conditions such as starving or prolonged fasts. A large portion of the food that we eat is converted by the body into glucose. The blood delivers the glucose throughout the body, but in order for it be transported inside most cells the hormone insulin is needed. Insulin comes from the endocrine pancreas, the organ that is largely responsible for regulating blood glucose levels. If the pancreas does not make sufficient insulin or cells are resistant to its activity of promoting glucose uptake, the blood glucose level becomes elevated. Uncontrolled blood glucose can lead to damage to many systems including the kidneys, eyes, nerves and blood vessels.
Types of Diabetes
There are three types of diabetes mellitus, Type I (previously referred to as Insulin Dependent Diabetes Mellitus, IDDM), Type II (previously referred to as Non-insulin Dependent Diabetes Mellitus, NIDDM), and gestational diabetes that occurs during pregnancy.
Type I diabetes represents approximately 5-10% of diabetic patients. It usually has a rapid onset and most frequently manifests in children and adolescents (juvenile onset). Type I diabetes is thought to result from the immune system mistakenly recognizing the insulin producing cells (beta-cells) in the pancreas as “foreign” and destroying them. Because the body cannot use the dietary glucose, the level in the blood is elevated, excess glucose is lost in the urine taking with it a large amount of water (resulting in frequent urination), and weakness, thirst and hunger result. Frequently weight loss is seen. The treatment for type I diabetes is insulin replacement.
A serious complication of type I diabetes is the development of ketoacidosis. As a result of cellular starvation, excessive fat breakdown causes the production of fatty acids that are converted into substances called ketone bodies. At high levels these substances are toxic. This condition most often occurs in adolescents that do not take their insulin as scheduled, but can also occur in the presence of infections or major forms of stress. There has also been concern that a large percentage of teenage girls with type I diabetes cut back on their insulin to promote weight loss. Proper use of insulin is vital for preventing short and long term complications.
Wordlwide, some 120 million Type II diabetics (adult onset) are able to produce insulin but the liver and muscle cells are resistant to its actions. Some type II diabetics can be effectively treated with diet alone, but many require oral medications. It is common for insulin to be needed as the disease progresses. Historically, this has been thought of as maturity onset diabetes because it tends to occur after age 50, but there has been a dramatic increase in the number of adolescents with the disease. This is thought to be due to increased obesity and decreased physical activity in this age group.
Gestational diabetes is diabetes that is first diagnosed during pregnancy. Hormones produced by the placenta oppose the action of insulin in order to provide food for the growing baby. In gestational diabetes, these hormones cause elevated blood glucose levels and can cause the baby to grow to a size larger than normal. This increases the risk for a difficult delivery. If diet alone is insufficient to provide blood sugar control, insulin is the treatment of choice. Some oral agents may be used during the 2nd or 3rd trimester, but they are not used during the 1st trimester since little is known about their effects on the developing baby at this critical stage.
Complications Commonly Associated with Diabetes
The risk of complications associated with diabetes can be largely decreased with proper blood glucose control and the maintenance of a healthy lifestyle. Early detection of complications by routine medical examination also increases the chances that the damage can be reversed or minimized. It is important for diabetics to be committed to taking an active role in their disease management.
The major complication of diabetes is damage to the heart and blood vessels, which can cause heart attacks, strokes, and poor circulation. These complications are associated not only with elevated blood glucose, but also elevated blood fat (cholesterol). Insulin is also involved in fat metabolism. Cholesterol at elevated concentrations tends to deposit in blood vessels, making them more narrow, thereby decreasing the delivery of oxygen and nutrients to tissues, and increasing the chance that a blood clot will form. Elevated blood glucose is associated with other cellular events that cause progressive narrowing of blood vessels. The effects on blood vessels also increase the risk of developing high blood pressure (hypertension).
Diabetics have an increased risk of eye disease. Damage to the retina associated with diabetes is the leading cause of blindness in adults under age 65 in the US. The retina is a layer of blood vessels and nerve endings on the back wall of the eye. Signals generated in the retina travel to the brain where vision is generated. Blood vessels in the retina may swell and leak fluid, or abnormal blood vessel growth may occur. These changes can impair vision or cause blindness. Poor blood glucose control also increases the risk of cataracts and glaucoma. It is important for diabetics to have their eyes examined yearly because the early stages of eye disease are often successfully treated but are generally not associated with symptoms.
When blood glucose is high, nerve cells swell and scar. Eventually their ability to send proper signals throughout the body is impaired. The disease associated with nerve damage to the nerves outside of the brain and spinal cord is referred to as peripheral neuropathy. The two most common types of neuropathy in diabetics involve impairment of sensory and autonomic nerves. Impaired nerve signals to the brain about sensations such as the detection of heat or pain may lead to burns or undetected cuts that can become infected. If untreated, infected foot and leg ulcers can spread to the bone and may require amputation. Daily examination of the feet to identify sores or cuts at an early stage often prevents this from occurring. Burning, pain or tingling sensations in the hands, legs and feet are also common.
Impairment of nerves that control involuntary activities of the body can affect processes such as digestion. Nerve damage can cause the stomach to empty too slowly and result in nausea and vomiting, bloating, and loss of appetite. Damage to nerves in the esophagus may impair swallowing, and damage to the intestines can cause constipation or diarrhea. Other common occurrences are impotence and impaired bladder emptying which increases the risk of bladder infections.
The kidneys are vital for ridding the body of toxic waste products, and maintaining fluid, mineral and electrolytes at levels compatible with life. Elevated blood glucose can damage the cells and small blood vessels of the kidney. The result is that the body retains toxins, and protein is lost in the urine. Symptoms of kidney failure include fatigue, decreased appetite, nausea and vomiting. Damage to the kidneys is not associated with symptoms at the early stages. A test to detect proteins in the urine is used as a screen to detect kidney damage. Controlling high blood pressure also decreases the risk of developing kidney disease. A certain class of high blood measure medication referred to as the angiotensin-converting enzyme inhibitors (ACE inhibitors), including Capoten®, Prinivil® and Accupril®, have been shown to reduce not only the risk of diabetic kidney disease but also heart attack and stroke. Advanced kidney damage results in the need for artificial filtration of the blood by dialysis and potentially the need for a kidney transplant.
Treatment of Diabetes
In some people, blood glucose levels can be successfully controlled with diet and exercise, but many people require insulin or oral tablets. Insulin injections are required when the pancreas fails to make sufficient insulin. Patients requiring insulin often show signs of diabetes at a young age. This is referred to as Type I diabetes. Diabetics whose pancreas makes insulin but develop elevated blood glucose levels due to resistance to the effects of insulin are often placed on oral tablets and diet therapy, although occasionally insulin injections are needed. These patients are often said to have Type II diabetes and represents the majority of diabetics (90-95%).
Many drugs interfere with diabetes treatments by directly affecting blood sugar levels. Diabetics may sometimes use these drugs, but a physician or pharmacist should be consulted before adding or discontinuing any over-the-counter or prescription drug. For example, certain diuretics, corticosteroids, phenytoin, isoniazid, large doses of aspirin, and estrogens, can increase blood sugar. Beta blockers (ex. Tenormin®, Lopressor®, Inderal®, Kerlone®), commonly used to treat conditions such as abnormal heart rhythms, migraines, and high blood pressure have multiple effects on blood glucose regulation. In addition, they may mask the symptoms associated with low blood sugar. Low blood sugar can have serious implications and diabetics and their families are educated to recognize the symptoms and instructed in appropriate actions to take.
Herbs or botanical products may also affect blood sugar. For example, garlic increases blood insulin levels, therefore increasing the risk of developing a low blood sugar. There is also some evidence that horse chestnut and black cohosh may increase the effects of oral antidiabetic medications.
Monitoring blood glucose control
An important part of successful diabetic care is achieved by patient monitoring of blood sugar levels at home. This allows the physician and patient to evaluate the success of the current treatment. The better the control, the less the risk of developing complications. In the past, the main interest was in controlling fasting blood sugar levels, but recent evidence suggests control of levels two hours after meals is also important in decreasing the risk of complications.
There are multiple types of glucose monitors available. Some of them have voice synthesizers that can be used to help visually impaired patients. Several monitors enable the blood to be drawn from areas other than the finger. A great advance in monitoring is the existence of a monitor that uses a small electric current to measure the glucose in the fluid under the skin instead of requiring a blood sample. Readings are taken every 20 minutes and an alarm sounds if the glucose falls outside of the normal range. Several other noninvasive devices are in development.
Regular blood tests to determine the concentration of hemoglobin A lc are used to determine if there has been adequate control of blood glucose levels. This test shows the average amount of glucose in the blood over the last three months. It is recommended to keep the hemoglobin A1c concentration less than seven percent. Studies have shown that this can significantly decrease the risk of developing complications from diabetes.