Yi-Hao Yu, MD, PhD
Board-certified internist
Clinical fellow in endocrinology
Columbia Presbyterian Hospital
New York, NY
I. What is diabetes?
Diabetes mellitus vs. diabetes insipidus. As we talk about “diabetes”, we may just refer to diabetes mellitus. There are some people who have diabetes insipidus, however. Patients with either diabetes mellitus or diabetes insipidus may have symptoms of polyuria and polydypsia, i.e., frequent urination and drinking, respectively. But each disease has a completely different cause, a different set of complications and treatment options.
Diabetes mellitus is a disease in which either the hormone insulin is lacking or the body’s cells are insensitive to insulin’s effects. Adequate insulin function is essential for life. This hormone allows many of body’s cells to use glucose as their energy source, without these cells are unable to sustain their lives.
Type 1, type2 and gestational diabetes. There are two types of diabetes mellitus, type 1 and type 2. Type 1 is characterized by a deficiency or absence of insulin due to destruction of the patient’s pancreatic islet cells (b-cells) by an autoimmune process. During this process the body makes antibodies that attack its own pancreas tissue. The onset of type 1 diabetes usually occurs early in life (most often during childhood and adolescence). The majority of diabetic patients are of type 2. Type 2 is characterized by insulin resistance, in which the cell’s response to insulin becomes blunted. In contrast to type 1, the onset of type 2 diabetes is usually much later in life (often over 40), and patients with type 2 disease are typically overweight. There are some young women who develop diabetes during their pregnancies, but it resolves promptly after delivery. This is called gestational diabetes. Usually these women require intensive insulin treatment during pregnancy to prevent fetal and maternal complications, but can be taken off medication completely after labor. They, however, have increased risk for developing type 2 diabetes later in their lives.
Genetics vs. environmental factors. Is diabetes mellitus inheritable? Yes and no. Both type 1 and type 2 may be genetically transmitted. But not all offspring of diabetic patients are diabetic, and many type 1 and some type 2 diabetic patients have no family history of the disease. This means environmental factors play an important role in bringing out diabetes in people who are born with a predisposition to the disease. Exactly what kinds of environmental factors trigger the development of diabetes are unknown, but certain types of viral infection and, sometimes, a history of pancreatitis may be important factors causing type 1 diabetes. On the other hand, increased food intake, obesity and sedentary life style are believed to be important risk factors for type 2 diabetes. In addition, people who receive treatment with corticosteroid drugs or who suffer Cushing’s syndrome are also prone to developing type 2 diabetes.
II. What kind of problems may diabetic patients run into?
Acute complications. First, since diabetic patients cannot adequately absorb and use glucose, which is converted from various food sources every time people eat, metabolic disturbances surely ensue. In type 1 diabetes, ketoacidosis is the most frequently encountered acute complication. In this situation, a group of chemical products called ketones build up and overwhelm the bloodstream. Excessive ketones are generated when body tissues use fat, instead of glucose, for energy. They cause the pH of the blood to shift downward due to the chemical’s acidity. Ketoacidosis develops more often in those who miss insulin doses or who are sick, because body’s requirement for insulin increases during any illness. If left untreated, ketoacidosis may quickly lead to coma and death. In type 2 diabetes, since there is still insulin on board (recall that the main problem in type 2 diabetes is the presence of insulin resistance), ketone-toxicity is of less a problem. But if the blood glucose level becomes too high, which promotes diuresis, and patients are inadequately repleted with water, then a hyperosmolar state may follow. This situation occurs most frequently in the elderly, the debilitated and the sick because they may be either unable to get water without assistance or unable to sense thirst because of their illness. When such a situation has developed, the blood may have become too “condensed”, and the concentrations of sodium and glucose in the bloodstream may reach unacceptable levels. This may also lead to so-called “nonketotic hyperosmolar coma” and death if untreated.
Long-term complications. The above two acute complications can be avoided as long as patients are able to take insulin in adequate amounts and keep themselves well hydrated (of course with unsweetened fluids only). What can be more difficult to most diabetic patients is to avoid long-term complications that may affect them five, ten, twenty or thirty years later in their lives. These complications include what’s called microvascular diseases, most notably affecting eyes (cataracts or proliferative retinopathy that may lead to blindness), kidneys (diabetic nephropathy which may lead to end-stage kidney failure necessitating life-long dialysis or kidney transplantation), nervous system (gastroparesis, postural hypotension and peripheral neuropathy with painful or numb limbs) and the skin (foot ulcers or gangrene). In these complications, the primarily affected are small blood vessels that run through these organs or tissues. Macrovascular complications affecting medium to large blood vessels are causes of stroke and heart attack. These complications are more profound in type 2 diabetes because of additional features of this disease, such as obesity, hypercholesterolemia and the blood’s hypercoagulable states. Not infrequently, men with diabetes may also suffer from impotence as part of the vascular complications.
III. How is diabetes diagnosed?
Common symptoms and signs. The most common symptoms of diabetes are frequent urination and, hence, increased thirst and excessive water drinking. There may also be unexplained weight loss, experiences of nausea, vomiting, abdominal pain or blurry vision. In type 1 diabetes, since there is an overwhelming amount of ketones in the blood which have a characteristic fruity odor, or a smell of nail-polish remover, people may be able to smell it from the patient’s breath.
Blood and urine tests. Diabetes is diagnosed and confirmed by blood and urine tests measuring glucose and ketones. Also measured sometimes are glycosylated hemoglobins, which are modified pigments in red blood cells that increase in concentration when blood glucose levels are high for the previous several weeks or months before the test. The current criteria for diagnosis of diabetes mellitus, developed by an international Expert Committee and adopted by the American Diabetes Association, is fasting plasma glucose equal to or above 126 mg/dl, with normal range being 75-110 mg/dl. People who have plasma glucose between 109 and 126 are classified as having impaired glucose tolerance, and their risk of developing type 2 diabetes later in life is much higher. In some instances, a special test called glucose tolerance test may be performed for diagnosis.
IV. How is diabetes treated?
Life-long commitment. There has been no cure for diabetes to date. This means, unfortunately, that diabetes has to be treated as a chronic disease with life-long commitment to management. Unlike an acute infection or a broken bone (fracture), which may be cured with a few week’s or month’s of treatment, this disease is much like hypertension, cardiovascular disease or other degenerative diseases in its chronicity. Pancreas transplantation is only occasionally offered to selected patients with type 1 diabetes, but this technique is still far from mature. Rejection is a serious problem, which may require life-long treatment with immune suppressant drugs.
Tight glucose control. In theory, as long as enough insulin is given regularly and blood glucose levels are controlled within or close to the normal range all the time, the disease should be under total control and patients are able to live a normal life. This is exactly our treatment goal is, and many diabetic patients do live a normal life! Even though we cannot completely reach this goal and, almost surely, are unable to adjust insulin and glucose levels the way the body normally does, we strive to make them as close to physiological conditions as possible. It has indeed been established by large and authoritative clinical trials - the Diabetes Control and Complications Trial (DCCT) and the United Kingdom Prospective Diabetes Study (UKPDS) - that the risk for microvascular complications in type1 and type 2 diabetes can be markedly reduced by tight glucose control. Although it has not been proven that the risk for macrovascular complications can also be reduced by tight blood glucose control, there have been many lines of putative evidence that suggest it may be so.
Insulin injection vs. oral medications. Depending on an individual’s life style, preference and other factors, type 1 patients may be treated with various insulin regimens via subcutaneous injection or insulin pump. The latter dispenses the hormone through a catheter that is inserted into the patients’ skin. Patients with type 2 diabetes usually have a much less severe insulin problem and therefore may not need insulin treatment, especially early in the course. Sometimes diet and exercise are all that are needed. Other times, pills taken orally are adequate to control blood glucose.
New drugs - “insulin sensitizers”. In type 2 diabetes, however, more needs to be done than just controlling glucose levels. Remember, what’s wrong in type 2 diabetes is predominantly insulin resistance. Thus, in order to obtain and utilize the same amount of glucose from the blood, a much larger amount of insulin is needed and, hence, a state of hyperinsulinemia (high blood insulin level) ensues. Many believe that weight gain, dyslipidemia, “thicker blood” (hypercoagulable state) and accelerated atherosclerosis may all be directly associated with hyperinsulinemia, since such an association appears to exist even when glucose levels are well controlled.
Until recently, type 2 diabetes was usually treated with diet, exercise and an oral hypoglycemic agent of the sulfonylurea family, such as glyburide and glipizide etc., which function to stimulate the pancreas to produce more insulin. If these measurements failed, doctors would proceed to an insulin regimen. Hyperinsulinemia associated with this disease would have never been specifically addressed.
Fortunately, new drugs have been developed to deal with this problem and more “insulin sensitizers” have been approved for type 2 diabetes. Available now are several new drugs of the thiazolidinedione family such as troglitazone (Rezulin), rosiglitazone (Avandia) and pioglitazone (Actos) as well as an older drug metformin (glucophage). These are drugs that function primarily to increase the sensitivity of the liver and other peripheral tissues to insulin’s effects, but not to increase insulin production. Therefore, therapy with these drugs allows a lower level of plasma insulin to achieve and maintain a normal glucose level. Such a treatment corrects hyperinsulinemia and, hence, may significantly reduce risk factors for accelerated atherosclerosis.
Patients with type 2 diabetes now have many more choices of initial treatment, not only for delaying the need for insulin injections, but also, perhaps more importantly, for reducing the risk of long-term complications. Certainly, all drugs have a given set of side effects, so patients need to consult their doctors regarding the risks and benefits of taking these drugs and deciding which regimen is most optimal for them.
V. How should diabetic patients take care of themselves?
The general life style. A healthy life style recommended for
other people is also good for patients with diabetes. A diet of fixed calories
containing complex carbohydrates (bread, rice, pasta and legumes) but low in
animal fat is particularly important for people with diabetes.
Patients should adopt a regular and moderate exercise program. There is
no need to cut moderate alcohol drinking, but tobacco use is detrimental to
health in many ways and should be discouraged.
Home glucose monitoring. Like many chronic diseases, daily care is crucial for the management of diabetes. As has been discussed previously, good glucose control on a daily basis is key to avoiding acute and long-term complications. In order to achieve this, patients who receive insulin therapy need home glucose monitoring (by finger stick) several times a day. Remember, there is usually no apparent sign or symptom sensitive enough to warn patients of a high level of glucose unless it becomes extremely high. But this doesn’t mean that a moderately high glucose level is okay. Frequent higher-than-normal glucose levels may be enough to do long-term damage to the micro- and macro-vesculature as discussed. Therefore, patients should not rely on their “instinct” (signs and symptoms) to guess what their daily glucose levels are, but rather should religiously follow finger stick results to guide their insulin administration if they wish to prevent accelerated long-term complications. Even for those who have had some complications, the same rules apply and tight glucose control will still significantly reduce the risk for further and worsening complications. Type 2 diabetic patients who are not using insulin but are taking pills should also periodically have their blood glucose or glycosylated hemoglobins checked and their therapy adjusted. When finger sticks are used, it’s important to appropriately record the numbers and indicate if they are fasting, premeal or two-hour postprandial glucose levels, so that they may be correctly interpreted by health care workers during office visits.
Preventing hypoglycemia. Patients with type 1 diabetes, or those with type 2 diabetes taking a sulfonylurea drug may occasionally develop life-threatening episodes of hypoglycemia, a state of very low blood glucose. In patients with type 1 diabetes, this usually occurs when a dose of insulin is excessive relative to the meal they take and it lowers blood glucose too much. In type 2 diabetic patients, hypoglycemia may be caused by gradual accumulation of a sulfonylurea drug in the blood, most often in patients who already have impaired kidney function that otherwise would excrete excessive amounts of the drug. When hypoglycemia has just developed, sweating, nausea, anxiety or tachycardia (rapid heartbeat) may appear. If these warning signs are not received by patients or are inappropriately ignored, confusion, seizure or coma may follow rapidly, and permanent brain damage or death can occur. To prevent hypoglycemia from happening, patients must balance their food intake (which increases glucose) with their dosages of insulin or hypoglycemic agents and physical activity (which decrease glucose). If a strenuous exercise is expected, for example, patients should do a finger stick, adjust insulin or eat more before exercise. Finally, patients should always carry with them candy or a glucagon injection kit for emergency use. Wearing a medical bracelet is also recommended to alert people in case of coma.
Vigilance about diabetic complications. In addition, diabetic patients should be vigilant about the potential to develop diabetic retinopathy. Patients should see an ophthalmologist once a year, or more often if there is already early eye disease, and they should receive appropriate treatment as needed to prevent a devastating complication – blindness. Patients should adapt a habit of checking their feet daily for any skin breakdown or ulcers, especially if they have already had some sensory impairment and are unable to feel pain or pressure in their feet. They should wear shoes that fit comfortably and cut toenails straight across, or have podiatrist visits on a regular basis. Doctors should be promptly consulted if a foot ulcer or infection is discovered. As far as the kidney is concerned, patients may remind their doctor to periodically order a urine test for early kidney disease, i.e., microalbuminemia. Drugs of the ACE inhibitor family are very effective in retarding the progression of diabetic kidney disease. Finally, patients with diabetes are also frequently dyslipidemic and hypertensive, and are taking multiple medications. But they should not be discouraged if another medication needs to be added to their existing medical regimen, or if the dose of some medications needs to be increased. At times it may become tremendously hard to follow a “routine” for various reasons, but patients should realize that each medication in their regimen may be extremely important for controlling individual risk factors and should be taken consistently in order to minimize the risk of stroke or heart attack.
Like many other chronic diseases, it is the very chronicity that frustrates patients the most. It is the daily vigilance and compliance that are the most difficult to maintain but which are most needed and will prove to be highly rewarding. Self-help groups exist in the US for affected people and may be sought out.