Diabetes is the name of two different diseases of the endocrine system, both characterized by excessive urination and thirst.
Diabetes mellitus affects carbohydrate, protein, and lipid metabolism. Diabetes insipidus is caused by an inability of the kidney to conserve water, due to a lack of antidiuretic hormone. This article discusses the far more prevalent diabetes mellitus.
Types of Diabetes Mellitus
Diabetes occurs when the pancreas is unable to secrete enough insulin to maintain a normal concentration of the sugar glucose in the blood. In severe cases the blood-glucose concentration is very high, and large amounts of glucose are excreted in the urine. Primary diabetes has two forms: insulin-dependent and noninsulin-dependent, both caused by environmental and genetic factors. Pancreas damage causes secondary diabetes.
Insulin-dependent diabetes generally starts in childhood and is characterized by severe insulin deficiency, probably due to the destruction of the insulin-secreting cells of the pancreas. Without insulin the person develops ketoacidosis (high levels of ketone bodies in the blood, causing lowered blood pH and possible heart failure) and coma (caused by the very high blood glucose levels).
The noninsulin-dependent form usually occurs in people over age 40. These people have higher than normal levels of insulin but are resistant to its action; ketoacidosis is rare. Obesity can impair insulin action, so obese people are predisposed to this form of diabetes, as are populations that have recently adopted Western processed-food diets. Some women develop elevated glucose levels during pregnancy and birth, called gestational diabetes. Glucose levels may return to normal after birth, but these women have an increased risk of developing noninsulin-dependent diabetes in the future.