Glucose Intolerance

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Basics

Description

  • Glucose intolerance is an intermediate stage between a normal glucose metabolism and diabetes.
  • Individuals with impaired fasting glucose (IFG) and/or impaired glucose intolerance (IGT) have been referred to as having prediabetes:
    • IFG: 100 to 125 mg/dL
    • IGT: 140 to 199 mg/dL 2 hours after ingestion of 75 g oral glucose load
    • Hemoglobin A1c (HbA1c) 5.7–6.4% (1)

Epidemiology

  • As of 2010, it is estimated that one of every three U.S. adults ≥20 years of age have prediabetes (2).
  • An estimated 86 million people in the United States are living with prediabetes.
  • Only 11% of people with prediabetes are aware of their condition (3).
  • Prediabetes has a 37% prevalence among adults >20 years old and 51% of adults ≥65 years in the United States (4).

Incidence
  • Systematic review indicates a 5-year cumulative incidence of developing diabetes of 9–25% for people with an HbA1c of 5.5–6.0% and 25–50% with an HbA1c of 6.0–6.5% (1).
  • Highest incidence in American Indians/Alaska Natives, non-Hispanic blacks, and Hispanics (2)

Prevalence
From 2009–2012, prevalence of pre-diabetes in the United States was 37% in adults > 20 years old and 51% in adults > 65 years old. According to ADA, in 2015 84.1 million Americans > 18 years old had pre-diabetes. As of 2010, worldwide prevalence was 8%.

Etiology and Pathophysiology

Progressive loss of insulin secretion on the background of insulin resistance (1)

Genetics
Genetic heterogeneity is the concept that diabetes and glucose intolerance can have many different causes. This was first suggested by existence of rare genetic syndromes that cause diabetes, also ethnic differences in clinical features and findings from animal models. It is now firmly established by family, twin, immunologic, and HLA disease association studies.

Risk Factors

  • Body mass index (BMI) ≥25: overweight
  • Obesity and metabolic syndrome
  • History of gestational diabetes mellitus (GDM)
  • Sedentary lifestyle
  • Medications (see “Differential Diagnosis”)
  • Genetic factors. Variants in 11 genes have been shown to be significantly associated with future development of type 2 diabetes and IFG. Variants in 8 of these genes have been associated with impaired β-cell function.

General Prevention

  • Lifestyle modification with weight reduction and increased physical activity
  • A decrease in excess body fat provides the greatest risk reduction.

Pregnancy Considerations

  • Screening for diabetes in pregnancy is based on risk factor analysis:
    • High risk: first prenatal visit
    • Average risk: 24 to 28 weeks’ gestation
  • Women with GDM should be screened for diabetes 6 to 12 weeks postpartum with 75-g OGTT and then every 1 to 3 years via any method (5).

Commonly Associated Conditions

  • Obesity (abdominal and visceral obesity)
  • Dyslipidemia with high triglycerides (TG)
  • Metabolic syndrome
  • PCOS
  • GDM
  • Low HDL
  • HTN
  • Congenital diseases (Down, Turner, Klinefelter, and Wolfram syndromes)

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Basics

Description

  • Glucose intolerance is an intermediate stage between a normal glucose metabolism and diabetes.
  • Individuals with impaired fasting glucose (IFG) and/or impaired glucose intolerance (IGT) have been referred to as having prediabetes:
    • IFG: 100 to 125 mg/dL
    • IGT: 140 to 199 mg/dL 2 hours after ingestion of 75 g oral glucose load
    • Hemoglobin A1c (HbA1c) 5.7–6.4% (1)

Epidemiology

  • As of 2010, it is estimated that one of every three U.S. adults ≥20 years of age have prediabetes (2).
  • An estimated 86 million people in the United States are living with prediabetes.
  • Only 11% of people with prediabetes are aware of their condition (3).
  • Prediabetes has a 37% prevalence among adults >20 years old and 51% of adults ≥65 years in the United States (4).

Incidence
  • Systematic review indicates a 5-year cumulative incidence of developing diabetes of 9–25% for people with an HbA1c of 5.5–6.0% and 25–50% with an HbA1c of 6.0–6.5% (1).
  • Highest incidence in American Indians/Alaska Natives, non-Hispanic blacks, and Hispanics (2)

Prevalence
From 2009–2012, prevalence of pre-diabetes in the United States was 37% in adults > 20 years old and 51% in adults > 65 years old. According to ADA, in 2015 84.1 million Americans > 18 years old had pre-diabetes. As of 2010, worldwide prevalence was 8%.

Etiology and Pathophysiology

Progressive loss of insulin secretion on the background of insulin resistance (1)

Genetics
Genetic heterogeneity is the concept that diabetes and glucose intolerance can have many different causes. This was first suggested by existence of rare genetic syndromes that cause diabetes, also ethnic differences in clinical features and findings from animal models. It is now firmly established by family, twin, immunologic, and HLA disease association studies.

Risk Factors

  • Body mass index (BMI) ≥25: overweight
  • Obesity and metabolic syndrome
  • History of gestational diabetes mellitus (GDM)
  • Sedentary lifestyle
  • Medications (see “Differential Diagnosis”)
  • Genetic factors. Variants in 11 genes have been shown to be significantly associated with future development of type 2 diabetes and IFG. Variants in 8 of these genes have been associated with impaired β-cell function.

General Prevention

  • Lifestyle modification with weight reduction and increased physical activity
  • A decrease in excess body fat provides the greatest risk reduction.

Pregnancy Considerations

  • Screening for diabetes in pregnancy is based on risk factor analysis:
    • High risk: first prenatal visit
    • Average risk: 24 to 28 weeks’ gestation
  • Women with GDM should be screened for diabetes 6 to 12 weeks postpartum with 75-g OGTT and then every 1 to 3 years via any method (5).

Commonly Associated Conditions

  • Obesity (abdominal and visceral obesity)
  • Dyslipidemia with high triglycerides (TG)
  • Metabolic syndrome
  • PCOS
  • GDM
  • Low HDL
  • HTN
  • Congenital diseases (Down, Turner, Klinefelter, and Wolfram syndromes)

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