Type 2 diabetes begins with insulin resistance, a condition in which cells fail to respond to insulin properly.[2] As the disease progresses, a lack of insulin may also develop.[12] This form was previously referred to as "non insulin-dependent diabetes mellitus" (NIDDM) or "adult-onset diabetes".[2] The most common cause is a combination of excessive body weight and insufficient exercise.[2]
The classic symptoms of untreated diabetes are unintended weight loss, polyuria (increased urination), polydipsia (increased thirst), and polyphagia (increased hunger).[22] Symptoms may develop rapidly (weeks or months) in type 1 diabetes, while they usually develop much more slowly and may be subtle or absent in type 2 diabetes. Other symptoms of diabetes include weight loss and tiredness.[23]
In 2017, 425 million people had diabetes worldwide,[9] up from an estimated 382 million people in 2013[18] and from 108 million in 1980.[104] Accounting for the shifting age structure of the global population, the prevalence of diabetes is 8.8% among adults, nearly double the rate of 4.7% in 1980.[9] [104] Type 2 makes up about 90% of the cases.[17][19] Some data indicate rates are roughly equal in women and men,[19] but male excess in diabetes has been found in many populations with higher type 2 incidence, possibly due to sex-related differences in insulin sensitivity, consequences of obesity and regional body fat deposition, and other contributing factors such as high blood pressure, tobacco smoking, and alcohol intake.[105][106]
Insulin is a hormone produced by cells in the pancreas called beta cells. Insulin helps the body use blood glucose (a type of sugar) for energy. People with type 2 diabetes do not make enough insulin and/or their bodies do not respond well to it, leading to elevated blood sugar levels. Oral diabetes medications bring blood sugar levels into the normal range through a variety of ways.
Recently, battery-operated insulin pumps have been developed that can be programmed to mimic normal insulin secretion more closely. A person wearing an insulin pump still must monitor blood sugar several times a day and adjust the dosage, and not all diabetic patients are motivated or suited to such vigilance. It is hoped that in the future an implantable or external pump system may be perfected, containing a glucose sensor. In response to data from the sensor the pump will automatically deliver insulin according to changing levels of blood glucose.
Extreme urination continues throughout the day and the night. In children, DI can interfere with appetite, eating, weight gain and growth, as well. They may present with fever, vomiting or diarrhea. Adults with untreated DI may remain healthy for decades as long as enough water is consumed to offset the urinary losses. However, there is a continuous risk of dehydration and loss of potassium that may lead to hypokalemia.
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