What is Insulin Resistance?
- Insulin is a hormone that is produced by the beta cells found in the pancreas.
- Insulin is an important hormone that has many actions within the body including those involved in metabolism (control) of carbohydrates (sugars and starches), lipids (fats), and proteins.
- When insulin resistance develops, tissues in the body – particularly muscle and fat tissues- do not respond appropriately to insulin. In fact, more insulin is needed to elicit the same response from these tissues.
- As a result, higher levels of insulin are needed in order for insulin to continue to exert its physiologic effect.
Insulin Resistance Causes
There are many causes of insulin resistance, including a strong association with genetics (an inherited component). In addition, insulin resistance is often associated with the following conditions:
Insulin Resistance Symptoms
Aside from the well known association of insulin resistance with the metabolic syndrome, abdominal obesity, elevated cholesterol levels, and high blood pressure; there are several other medical conditions that are associated with insulin resistance specifically. While the associations are clear, whether insulin resistance is the cause of these conditions is not yet known.
Type 2 Diabetes
While insulin resistance is usually seen long before diabetes develops, in cases in which medical attention has lapsed, insulin resistance can present as type 2 diabetes.
The accumulation of fat in the liver is a manifestation of the disordered control of lipids that occurs with insulin resistance. The extent of liver damage can range from mild to severe. Newer evidence suggests that fatty liver may even lead to cirrhosis of the liver, and possibly liver cancer.
Insulin resistance is one of the factors associated with arteriosclerosis. Arteriosclerosis, also known as atherosclerosis, is a process of progressive thickening and hardening of the walls of medium-sized and large arteries. Arteriosclerosis is responsible for:
Skin lesions include an increased number of skin tags and a condition called acanthosis nigricans - a darkening and thickening of the skin, especially in fold areas such as the neckline and axilla. This condition is directly related to the insulin resistance, though the exact causal mechanism is not known.
Reproductive abnormalities in women
Reproductive abnormalities include difficulty with ovulation and conception (infertility), irregular menses, or a cessation of menses. A condition that is significantly associated with insulin resistance is polycystic ovary syndrome (PCOS). PCOS is a problem that affects young women. It is associated with irregular periods or no periods at all, obesity, and increased growth of body hair. In contrast to women, there are no known reproductive abnormalities in men associated with insulin resistance.
High levels of male hormones in women, which are produced by the ovaries, can been seen in insulin resistance and may play a role in PCOS as described above. The high levels of insulin seen in insulin resistance causes the abnormal ovarian hormone production of testosterone and other hormones.
There may be growth effects in insulin resistance due to the high levels of circulating insulin that may be present. While insulin's effects on glucose metabolism may be impaired, its effects on other mechanisms may be intact (or at least less impaired). Insulin can exert effects on growth, through a mediator known as insulin- like growth factor -1. Individuals may have actual linear growth in height and a noticeable coarsening of features. The increased incidence of skin tags mentioned above may be due to this mechanism as well.
Medically Reviewed by a Doctor on 5/11/2016
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