Metabolic syndrome is believed to develop due to insulin resistance. Insulin is a hormone that is produced by the pancreas (an organ located near stomach). It helps blood sugar enter cells, where it is used for energy. With insulin resistance, the body fails to recognize the insulin that is produced, causing the sugar to accumulate in the blood instead of being absorbed into other cells. Because blood sugar levels remain high, the pancreas keeps producing more and more insulin, leading to high insulin levels. While blood sugar levels are not high enough to be classified as diabetes, they do increase the risk of developing serious health problems.

^ Jump up to: a b c d e f Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo Jr. JL, Jones DW, Materson BJ, Oparil S, Wright Jr. JT, Roccella EJ, et al. (December 2003). "Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure". Hypertension. Joint National Committee On Prevention. 42 (6): 1206–52. doi:10.1161/01.HYP.0000107251.49515.c2. PMID 14656957. Archived from the original on 20 May 2012. Retrieved 1 January 2012.

When there is excess glucose present in the blood, as with type 2 diabetes, the kidneys react by flushing it out of the blood and into the urine. This results in more urine production and the need to urinate more frequently, as well as an increased risk of urinary tract infections (UTIs) in men and women. People with type 2 diabetes are twice as likely to get a UTI as people without the disease, and the risk is higher in women than in men.
Metabolic syndrome is increasing in prevalence, paralleling an increasing epidemic of obesity. In the United States, where almost two thirds of the population is overweight or obese, more than one fourth of the population meets diagnostic criteria for metabolic syndrome. [25] In the United States, data from a 1999-2000 survey showed that the age-adjusted prevalence of metabolic syndrome among adults aged 20 years or older had risen from 27% (data from 1988-1994) to 32%. [26]
Because metabolic syndrome and insulin resistance are closely tied, many healthcare providers believe that insulin resistance may be a cause of metabolic syndrome. But they have not found a direct link between the two conditions. Others believe that hormone changes caused by chronic stress lead to abdominal obesity, insulin resistance, and higher blood lipids (triglycerides and cholesterol).
Insulin is vital to patients with type 1 diabetes - they cannot live without a source of exogenous insulin. Without insulin, patients with type 1 diabetes develop severely elevated blood sugar levels. This leads to increased urine glucose, which in turn leads to excessive loss of fluid and electrolytes in the urine. Lack of insulin also causes the inability to store fat and protein along with breakdown of existing fat and protein stores. This dysregulation, results in the process of ketosis and the release of ketones into the blood. Ketones turn the blood acidic, a condition called diabetic ketoacidosis (DKA). Symptoms of diabetic ketoacidosis include nausea, vomiting, and abdominal pain. Without prompt medical treatment, patients with diabetic ketoacidosis can rapidly go into shock, coma, and even death may result.