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Insulin Resistance Syndrome Type A and Type B
Insulin resistance is a common problem and one that can be a harbinger of future medical problems such as type 2 diabetes and heart disease. It is a condition where the body becomes less sensitive to the effects of insulin, the hormone produced by the pancreas that helps regulate glucose levels by ferrying glucose out of the bloodstream and into cells where it can be used for energy. When cells don’t respond as readily to insulin, blood levels of glucose rise in the blood, which is an unhealthy situation. There are actually two types of insulin resistance – insulin resistance syndrome type A and type B. How do these two types differ?
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Type A Insulin Resistance
For insulin to do its job of helping glucose enter cells, it must first bind to special insulin receptors on the surface of these cells. With type A diabetes, insulin can’t bind as well because insulin receptors are either absent or they are not functioning properly. This is usually because there’s a mutation in the genes that code for the insulin receptors so that the receptors are defective and can’t bind insulin as well. When this happens, the body responds by pumping out more insulin in a fevered attempt to get glucose into the energy-hungry cells. In some cases, the body doesn't compensate by producing more insulin. This leads to elevated blood sugar levels and type 2 diabetes.
People who have type A insulin resistance due to bad insulin receptors may have certain characteristics. Type A insulin resistance generally occurs at a younger age than type B, and people who have it may be tall and muscular or thin. Some may have large hands and feet and a prominent jaw similar to people with too much growth hormone. They may also have excess body hair.
Women who have type A insulin resistance are also more prone to polycystic ovary disease, a condition where they have many small cysts on their ovaries, high levels of male hormones called androgens and irregular menstrual periods.
Another clinical characteristic of people with type A insulin resistance is a condition called acanthosis nigrans where skin folds become darkly pigmented with a velvety texture. The back of the neck and under the arms are common spots where you might see acanthosis nigrans due to insulin resistance.
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Type B Insulin Resistance
Unlike type A insulin resistance where the insulin receptors are dysfunctional or absent due to gene mutations, type B insulin resistance occurs when antibodies are produced against the insulin receptors. When antibodies are directed against the receptors, it blocks them and insulin can’t bind as well. This causes insulin levels to rise and, in many cases, blood sugar too. People with type B can also have symptoms of hypoglycemia or low blood sugar since the antibodies produced against the insulin receptor sometimes mimic the effects of insulin. Needless to say, blood sugars can be very difficult to control with this type of insulin resistance.
Type B insulin resistance is less common than type A and is more frequently seen in African Americans. Since the cause of type B insulin resistance is autoimmune from antibodies produced against the insulin receptor, doctors sometimes use drugs that suppress the immune response or a procedure called plasmapharesis that removes some of the antibodies. People with this type of insulin resistance also have another autoimmune disease in as many as one-third of cases.
People with type B insulin resistance may have the same symptom of acanthosis nigrans as those with type A insulin resistance experience. Women may also have elevated levels of androgens, and they may have another autoimmune condition such as autoimmune thyroid disease or SLE.
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Insulin Resistance Syndrome Type A and Type B: The Bottom Line?
Type A insulin resistance is more common than type B and is usually easier to treat. Type B insulin resistance often requires drugs that suppress the immune system to help get blood sugar and insulin levels under control. If you have insulin resistance syndrome, these are all issues you’ll want to discuss with your doctor.
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E-medicine. "Insulin Resistance"
The Journal of Clinical Endocrinology & Metabolism Vol. 95, No. 8 3641-3647.
Merck Manual. Eighteenth edition. 2006.