If left untreated, diabetes mellitus may cause life-threatening complications. Type 1 diabetes can result in diabetic coma (a state of unconsciousness caused by extremely high levels of glucose in the blood) or death. In both Type 1 and Type 2 diabetes, complications may include blindness, kidney failure, and heart disease. Diabetes can cause tiny blood vessels to become blocked; when this occurs in blood vessels of the eye, it can result in retinopathy (the breakdown of the lining at the back of the eye), causing blindness. Diabetes mellitus is the leading cause of new cases of blindness in people aged 20 to 74. When diabetes affects the kidney it is called nephropathy (the inability of the kidney to properly filter body toxins). About 40 percent of new cases of end-stage renal disease (kidney failure) are caused by diabetes mellitus. Blockages of large blood vessels in diabetics can lead to many cardiovascular problems, including high blood pressure, heart attack, and stroke. Although these conditions also occur in nondiabetic individuals, people with diabetes are two to four times more likely to develop cardiovascular disorders.
Hypoglycemia, condition characterized by an abnormally low level of sugar in the blood. Symptoms of hypoglycemia include weakness, shakiness, nervousness, anxiety, and faintness and actual fainting. Patients also may show marked personality changes and may seem intoxicated. Hypoglycemia is the result of hyperinsulinism, or an excess of insulin, due either to an overdose of insulin—in the case of persons with diabetes mellitus—or to the body's overproduction of insulin. Insulin is instrumental in regulating carbohydrate metabolism; when hyperinsulinism occurs, glucose is sharply depleted in the process of conversion to glycogen in the liver and muscles and to fat in the adipose tissues.
Reactive, or functional, hypoglycemia—the most common type—occurs particularly among persons under emotional stress. It is also due to overproduction of insulin, commonly three to five hours after meals. Its symptoms are milder than those suffered by insulin-dependent diabetics, and it can be controlled by lowering carbohydrate intake. Because reactive hypoglycemia has many of the classical symptoms of depression or anxiety, it is often wrongly believed to be the cause of underlying psychological disorders. Even when this physical condition is properly diagnosed, it is most often found to be incidental to, rather than the direct cause of, the patient's symptoms.
Diabetes mellitus may also cause loss of feeling, particularly in the lower legs. This numbness may prevent a person from feeling the pain or irritation of a break in the skin or of foot infection until after complications have developed, possibly necessitating amputation of the foot or leg. Burning pain, sensitivity to touch, and coldness of the foot, conditions collectively known as neuropathy, can also occur. Other complications include higher-risk pregnancies in diabetic women and a greater occurrence of dental disease.
The association between diabetes mellitus and osteoporosis remains controversial. Although the metabolic abnormalities of diabetes potentially affect bone metabolism, structure, and mineral density, it is not clear if these changes are responsible for the increase in fracture risk noted in individuals with type 1 and type 2 diabetes. Children and adolescents with type 1 diabetes have reduced bone mineral density (BMD) at the forearm which appears constant with time. The majority of studies in type 2 diabetes have found that BMD is normal or increased at the lumbar spine, femoral neck, and mid and distal radius. These findings applied to both women and men. As expected, BMD correlated with body mass index
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