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Insulin resistance

OVERVIEW

What is insulin resistance?

Insulin resistance refers to a condition where the effectiveness of insulin in the liver, muscles, and adipose tissue is weakened due to various reasons, leading to impaired glucose uptake by peripheral tissues and reduced suppression of glucose output by the liver[1]. This results in elevated blood sugar levels, while insulin levels in the blood may remain normal or increase[2].

Insulin is a hormone secreted by pancreatic β-cells and plays roles such as lowering blood sugar, promoting protein and fat synthesis. It facilitates glucose uptake and utilization or storage in muscles and adipose tissue, while also inhibiting excessive glucose output by the liver to prevent abnormally high blood sugar levels[3].

Who is more likely to develop insulin resistance?

Insulin resistance tends to occur more frequently in the following groups:

  1. Obese individuals: Particularly those with abdominal obesity, where waist circumference exceeds 101.6 cm in men or 88.9 cm in women.
  2. Sedentary individuals: Such as office workers who remain inactive for long periods.
  3. People with high blood sugar: Fasting blood glucose levels above 100 mg/dL.
  4. Individuals with elevated blood pressure: Blood pressure levels exceeding 130/80 mmHg.
  5. Those with high blood lipids: Fasting triglyceride levels above 150 mg/dL[4,5].

SYMPTOMS

What are the common manifestations of insulin resistance?

In the early stages, insulin resistance may present no symptoms[5]. When it affects blood sugar levels or coexists with other underlying conditions, the following symptoms may occur[6]:

  1. Abnormal blood sugar: Individuals with insulin resistance often exhibit high blood sugar, leading to discomfort such as hunger and thirst. In response, pancreatic β-cells secrete more insulin to compensate for reduced effectiveness, resulting in elevated blood insulin levels (hyperinsulinemia), which may trigger hypoglycemia, manifesting as palpitations, dizziness, and sweating.
  2. Skin changes: Dark, velvety, thickened skin patches may appear in areas like the armpits, groin, and neck, known as acanthosis nigricans.
  3. Other symptoms: Women may also experience hirsutism, amenorrhea, and infertility, which are associated with polycystic ovary syndrome (PCOS).

Can insulin resistance lead to serious consequences?

Yes.

  1. Diabetes: Insulin resistance is one of the mechanisms contributing to type 2 diabetes (symptoms include increased thirst and hunger).
  2. Involvement in other diseases: It plays a role in the development of hypertension (systolic blood pressure ≥ 140 mmHg with or without diastolic blood pressure ≥ 90 mmHg), hyperlipidemia (fasting triglyceride levels exceeding 150 mg/dL), non-alcoholic fatty liver disease (symptoms may include loss of appetite and dull pain in the upper right abdomen), gout (joint pain and yellowish-white nodules around joints), and cardiovascular diseases (such as coronary heart disease, which may cause angina lasting several minutes). It can also affect height (significantly delayed growth compared to peers)[4,6,7].

Additionally, high blood sugar, hypertension, and hyperlipidemia can further exacerbate insulin resistance[4].

CAUSES

What are the common causes of insulin resistance?

Insulin resistance is associated with genetics (Type A insulin resistance), inflammation, obesity, physical inactivity, age (over 45), and other factors. A condition called "Type B insulin resistance syndrome" is related to autoimmune disorders[4,6].

  1. Genetics: Type A insulin resistance is caused by inherited defects in the insulin signaling pathway, preventing insulin from functioning properly in cells and tissues.
  2. Inflammation: Inflammatory responses in the body, such as rheumatoid arthritis, can increase the risk of insulin resistance to some extent.
  3. Obesity: Excess body fat releases excessive adipocytokines, triggering inflammation linked to insulin resistance and leading to the condition.
  4. Physical inactivity: Sedentary behavior increases the risk of insulin resistance, though the exact mechanism remains unclear.
  5. Age: The risk of insulin resistance rises after the age of 45, though the precise reason is unknown.
  6. Autoimmune disorders: When autoantibodies block insulin receptors, causing immune dysregulation, Type B insulin resistance syndrome occurs.

Is insulin resistance hereditary?

Yes. Hereditary insulin resistance has a genetic predisposition[8].

DIAGNOSIS

What tests are needed to diagnose insulin resistance?

Since there is no single test for diagnosing insulin resistance, clinical diagnosis typically involves a comprehensive evaluation of multiple factors[8], including body weight, blood lipids, blood pressure, blood uric acid, oral glucose tolerance test (OGTT), insulin release test, liver ultrasound, etc.[4,9].

  1. Body weight: Assess whether there is overweight (body mass index (BMI) of 24–28 kg/m²) or obesity (BMI ≥28 kg/m²), calculated as weight (kg) divided by [height (m)]2[9].
  2. Blood lipids and uric acid: Evaluate for hyperlipidemia (fasting triglyceride levels >150 mg/dL) or hyperuricemia (blood uric acid >420 µmol/L)[7].
  3. Blood pressure: Check for hypertension (systolic blood pressure ≥140 mmHg with or without diastolic blood pressure ≥90 mmHg)[7].
  4. Oral glucose tolerance test (OGTT): Assess for diabetes by measuring blood glucose after oral glucose intake[7].
  5. Insulin release test: A relatively accurate method to evaluate insulin resistance by measuring insulin levels after oral glucose intake[1].
  6. Liver ultrasound: Check for non-alcoholic fatty liver disease (NAFLD)[7].
  7. Hyperinsulinemic-euglycemic clamp: The "gold standard" for diagnosing insulin resistance, but mainly used in research and not widely available in clinical practice[6].
  8. If polycystic ovary syndrome (PCOS) is suspected: Additional tests such as sex hormone levels and ovarian ultrasound may be required[7].

What precautions should be taken during an insulin release test?

  1. Fast for at least 8 hours starting the night before the test.
  2. Drink 75 g of glucose dissolved in 250–300 mL of warm water (20–25°C) within 3–5 minutes.
  3. Follow medical instructions, cooperate with nurses for venous blood collection in a fasting state, and remain at rest during the test. Avoid smoking, strenuous exercise, or emotional excitement.
  4. Inform the doctor and reschedule the test if experiencing discomfort such as a cold, fever, or diarrhea before the examination[10].

TREATMENT

Which department should I visit for insulin resistance?

Endocrinology.

How is insulin resistance treated?

Insulin resistance is generally treated through lifestyle changes or medication[7-9,11]. Details are as follows:

  1. Lifestyle:
    • Healthy diet: Avoid excessive carbohydrate intake (e.g., reduce consumption of steamed buns, bread, etc.), limit red meat (e.g., beef, pork) and fried foods. It is recommended to eat more vegetables (e.g., spinach, cucumber), fruits (e.g., apples, citrus), fish, and poultry.
    • Physical activity: Engage in moderate-intensity exercise regularly, generally recommended for at least 150 minutes per week, with a daily goal of 6,000 steps.
    • Weight control: Aim for a body mass index (BMI), calculated as weight (kg) divided by [height (m)]2, between 20–25 kg/m2.
  2. Medication: There are currently no drugs specifically targeting insulin resistance. Medications for related conditions are often used to indirectly address insulin resistance.
    • Antidiabetic drugs: Such as metformin and pioglitazone, which help control blood sugar and improve insulin sensitivity. Common side effects include nausea and diarrhea.
    • Antihypertensive drugs: Such as betaxolol and metoprolol, which help control blood pressure. Common side effects include bradycardia (heart rate <60 beats per minute) and fatigue.
    • Statins: Such as atorvastatin and simvastatin, which help manage blood lipids. Side effects are rare but may include muscle pain and liver damage.

Note: While medications may have side effects, patients should not be overly concerned. Follow the doctor's instructions, maintain good communication, and adhere to the treatment plan.

Is follow-up necessary after insulin resistance treatment? How is insulin resistance monitored?

Yes, follow-up is required.

The timing of follow-up should be determined based on the doctor's recommendations. After treatment, regular monitoring of weight, blood pressure, blood sugar, blood lipids, plasma insulin, and other indicators is necessary to ensure treatment effectiveness, such as maintaining a BMI between 20–25 kg/m2[9].

Can insulin resistance be cured?

No, it cannot be cured. There is no evidence that insulin resistance can be completely cured; it can only be alleviated or improved.

DIET & LIFESTYLE

What should insulin-resistant patients pay attention to in their diet?

  1. Control daily total calorie intake. Consult a doctor, who will develop different dietary plans based on height, weight, blood sugar, and lipid levels[5].
  2. Avoid saturated fats (such as animal offal), trans fats (such as fried foods), carbonated beverages, concentrated fruit juices, and other high-sugar, high-fat foods[8].
  3. It is recommended to eat more foods that have a lower impact on blood sugar levels, such as dairy products, fish, apples, etc.[8].

Can insulin-resistant patients conceive normally?

Yes.

Insulin resistance can cause ovulation disorders in female patients, such as polycystic ovary syndrome. After treatment restores normal ovulation, normal conception is possible[7].

PREVENTION

Can Insulin Resistance Be Prevented?

Hereditary insulin resistance cannot be prevented; acquired insulin resistance (caused by non-genetic factors) can be prevented as follows:
Acquired insulin resistance can be partially prevented through methods such as a scientific diet (e.g., reducing sugary drinks), moderate exercise (e.g., walking 6,000 steps daily), maintaining a normal weight—where weight (kg) divided by [height (m)]2 is kept between 20–25 kg/m2[8,9,11].