Insulin resistance occurs in people who have an inability to properly use insulin, the hormone that moves glucose from the bloodstream into the cells. Normally, when a person eats, food is digested down into glucose that is absorbed into the bloodstream. As blood glucose levels start to rise, the pancreas, an organ behind the stomach, responds by secreting insulin.

Insulin moves glucose from the bloodstream into the cells and acts like a key that opens the door to the cell. Insulin allows glucose to enter the cells so that it can be converted to energy for the body to use. In addition, insulin also controls the rate at which the liver produces and secretes glucose (broken down from stored glycogen) between meals.

People with insulin resistance have muscle, fat and liver cells that do not respond properly to the effects of insulin. This prevents glucose from entering the cells therefore causing a buildup of glucose in the bloodstream. The body tries to compensate by producing more insulin, which causes hyperinsulinemia.

Insulin resistance may contribute to high blood glucose levels (hyperglycemia) in all types of diabetes. However, insulin resistance plays a greater role in certain types of diabetes:

• • Type 2 diabetes. Insulin resistance factors strongly in type 2 diabetes. It is believed that obesity and genetic factors linked to family history cause cells to become more resistant to insulin over time. The increased resistance leads to a greater likelihood that the individual will develop type 2 diabetes.
    
    
  • Gestational diabetes.  Insulin resistance may be present with this temporary form of diabetes that occurs during pregnancy. Certain hormones are released during pregnancy that can cause insulin resistance in the woman.
    
    
• Type 1 diabetes. For most individuals, insulin resistance is not a major factor in type 1 diabetes.  People with this autoimmune disease have problems producing insulin rather than using insulin. In some instances, however, people with type 1 diabetes can develop insulin resistance, causing a condition known as double diabetes. Double diabetes is more likely to appear in patients who are overweight or obese.

In addition, insulin resistance is often associated with the following conditions:

• Prediabetes. A condition in which a patient’s glucose level is consistently higher than normal but not high enough to be diagnosed as diabetes. This condition is also known as impaired fasting glucose, impaired glucose tolerance and glucose intolerance.
  
  
• Metabolic syndrome. Also known as insulin resistance syndrome and syndrome X. This syndrome refers to a cluster of conditions that can include:
  
  
• • Insulin resistance and hyperinsulinemia
  • High blood pressure
  • Blood lipid irregularities (insufficient HDL cholesterol, excess triglycerides)
  • Abdominal obesity

People with these characteristics are at a much higher risk of developing type 2 diabetes and heart disease.

• Polycystic ovarian syndrome (PCOS). A condition that affects women and is characterized by elevated male hormone levels (testosterone), absence of ovulation, irregular menstrual cycles and infertility. One woman in 10 has PCOS, according to the American Association of Clinical Endocrinologists. This condition substantially increases the risk for type 2 diabetes and cardiovascular disease.
  
  
• Acanthosis nigricans. A skin condition marked by darkening and thickening of skin in body creases. 

Insulin resistance has also been linked to heart conditions including coronary artery disease and heart failure. In addition, recent research suggests that insulin resistance may be a factor in the association of pancreatic cancer with type 2 diabetes.

Severe, sudden stress or trauma, such as burns, can also cause insulin resistance.

Initially, insulin resistance leads to high blood glucose levels immediately after meals. Over time, these high levels are present even in the fasting state. Chronic hyperglycemia leaves people more vulnerable to developing prediabetic conditions, diabetes and other potentially serious health problems.