Insulin is an essential hormone that is produced in the pancreas by beta cells. The body releases insulin in small amounts every time a meal is eaten so that glucose can be spread throughout the body. Glucose is essential to produce energy and is required by cells for survival. Bodies can demonstrate insulin resistance, which means cells, fat, and muscle tissue are less likely to respond to insulin’s effects. When someone is insulin resistant, their body will try to make up for a lack of insulin by producing even more of the hormone. This calls the blood to have inflated levels of insulin, creating a condition called hyperinsulinemia. It can also cause issues to be overstimulated, especially if those tissues are still sensitive to insulin. If not treated, this can cause glucose and insulin to become imbalanced in the body, which can lead to serious health issues.
Both insulin resistance and hyperinsulinemia are linked to the amount and concentration of lipids in the body. It can cause people to have more low-density lipoprotein and triglycerides in their bloodstream, as well as a decreased amount of high-density lipoprotein. This can create unhealthy cholesterol levels. Also, it can cause the body to retain more sodium, increase the risk for blood costs, and cause the body to become inflamed.
Experts do not fully understand what causes the body to develop a resistance to insulin. It’s believed that there are many factors in play, including a person’s lifestyle, ethnicity, and genetic predisposition to insulin resistance. Most people that are resistant to insulin do not show symptoms. The body can produce the additional insulin needed for years or more. However, when the body is not able to produce insulin as required, it can enter a hyperglycemic state. If glucose levels are elevated high enough, the body will develop type 2 diabetes. Anyone with insulin resistance is at increased risk for type 2 diabetes. This can cause blood vessels in numerous organs to be damaged, such as the vessels in the kidneys. Fatty plaque deposits can also form in the arteries due to these lipid changes, which can cause strokes and cardiovascular disease.
The term “insulin resistance” is often used interchangeably with “metabolic syndrome” to describe some of the issues that can occur when the body is insulin resistant and producing additional insulin. Both conditions can increase the risk of developing certain diseases. However, it’s more accurate to categorize metabolic syndrome as a subgroup of insulin resistance. The diagnostic criteria for metabolic syndrome include lipid level changes, issues with glucose processing, and obesity. The reason healthcare providers screen for metabolic syndrome is to identify the problem early on so that risks can be reduced through lifestyle changes.
Insulin resistance is not categorized as a disease, and because of this, it does not have specific diagnostic criteria. With that said, it is associated with numerous medical conditions, including obesity, type 2 diabetes, cardiovascular disease, polycystic ovarian syndrome, fatty liver disease, and hypertension. Some experts believe some types of cancer may be connected to insulin resistance. However, this is something that must be researched more extensively. Not all people that suffer from the conditions above are resistant to insulin. There are also people with insulin resistance that do not have any of these conditions. There is simply a link between insulin resistance and these health conditions. It is believed that insulin resistance could cause these issues to develop or make these issues more severe.
Insulin resistance isn’t something that can be detected through a single test. However, healthcare providers may suspect insulin resistance is a patient showing specific symptoms, such as elevated levels of glucose, LDL cholesterol, and triglycerides, while concentrations of HDL cholesterol decrease. Some of the tests a provider may order include:
Glucose Testing: Usually, this test requires fasting. However, other tests could be ordered as well, such as a glucose tolerance test, which is a series of tests that are taken at designated intervals. The purpose of this type of testing is to see if the body’s response to glucose is impaired.
A1C Testing: This test measures the percentage of hemoglobin that has bound to glucose in the bloodstream over the last three months. This test may also be referred to as a glycohemoglobin or HbA1c test.
Lipid Profile: This looks at the levels of triglycerides, HDL, and LDL in the body, as well as total cholesterol levels. If the test shows a significant elevation in triglyceride levels, LDL may be measured more directly.
Insulin resistance is frequently detected through the homeostatic model assessment. This measures the levels of insulin and glucose in the body, then uses that to calculate how pancreas beta cells are functioning.
Additional tests could be ordered to determine levels of insulin resistance and gather essential information could include:
Insulin testing: While results from a fasting test can vary, it’s typical for people with severe insulin resistance to show elevated levels
hs-CRP testing: This can evaluate cardiac risk by looking at low levels of inflammation in the body. Insulin resistance can cause an increase in inflammation.
LDL-P testing: This measures the number of low-density lipoprotein particles in the body via lipoprotein sub-fractions testing. It’s believed that certain types of LDL particles, such as small and dense particles, are linked to an increased risk for cardiovascular disease.
Insulin tolerance testing: Although this type of testing isn’t common, it’s one way to determine how sensitive to insulin a person is. The test is especially useful for people that are obese or suffering from PCOS. During the test, a person will receive an infusion of insulin via an IV. From there, levels of insulin and glucose will be measured.
Quantitative insulin sensitivity check index testing: Also known as QUICKI testing, this test calculates insulin resistance using a formula that uses a person’s glucose and insulin levels. Blood tests will need to be performed to gather the information necessary for these calculations.
In research environments, insulin suppression tests may be used, but these tests aren’t typical in clinical environments.