Dr. Keith Roach
Dear Dr. Roach: What are the main causes of insulin resistance? I was diagnosed with type 2 diabetes about 5 years ago. I have kept my weight constant under 200 pounds and am only 5 feet 9 inches tall. Last summer I was able to get my A1C levels up to 7.2%, but in late fall my numbers started to skyrocket even though I was using insulin. I now realize that I am injecting abnormal amounts of insulin just to maintain normal blood sugar levels.
I'm on a diet of 40 grams of carbohydrates a day. I walk nearly 20,000 steps a day. But on a typical day, he injects 30 to 40 units of insulin at mealtime, before a low-carbohydrate, high-protein meal. Still, my levels spike above 250 mg/dL and stay there for several hours.
— ARN
DEar ARN: Insulin is a signal that there is enough sugar in the body, and the body uses insulin to move sugar from the blood into the cells. Usually, administering a small amount of insulin can significantly lower blood sugar levels. When large amounts of insulin are required to lower blood sugar levels, insulin resistance is said to exist. Much research has been conducted to understand why people develop insulin resistance.
Rarely, there are congenital cases with mutations in the insulin receptor. Rarely, there are also acquired immune-mediated causes in which people have antibodies against insulin or the insulin receptor and are extremely resistant to insulin.
However, most cases of insulin resistance are associated with obesity. Your BMI is 29.5, suggesting that you are overweight but not obese. In this case, abdominal fat is metabolically more important because it can produce free fatty acids and compounds called adipocytokines, which can contribute to insulin resistance.
People with abdominal obesity and insulin resistance often have abnormal cholesterol levels and high blood pressure, a condition called “metabolic syndrome.” Blood pressure and cholesterol often need to be treated independently.
Insulin works to lower blood sugar levels, but there are four main hormones that counteract insulin and raise blood sugar levels: cortisol, catecholamines, glucagon, and growth hormone. Elevated levels of any of these cause insulin resistance. I know this is not your case, but the pregnancy hormone, human placental lactogen, causes insulin resistance and is the main cause of gestational diabetes.
Some drugs (steroids, oral contraceptives, HIV drugs) can cause insulin resistance. Importantly, glucose itself can cause insulin resistance. High blood sugar levels also inhibit insulin secretion. Therefore, it is very important to obtain and maintain normal blood sugar levels, especially when first diagnosed.
Managing people with high levels of insulin resistance can be difficult. It sounds like you're already doing amazingly well with your exercise, and your diet seems to be of the type commonly recommended. To reduce insulin use, drugs that lower insulin levels, such as metformin, GLP-1 agonists, and thiazolidinediones, are often recommended.
Since your situation is not common, it is imperative that you see an endocrinologist who specializes in diabetes.
Readers can email questions to ToYourGoodHealth@med.cornell.edu.