Diabetes Mellitus, Type 2

Key Features

Essentials of Diagnosis

• Typically > 40 years of age

• Obesity

• Polyuria and polydipsia

• Candidal vaginitis sometimes an initial manifestation

• Often few or no symptoms

• After an overnight fast, plasma glucose ≥ 126 mg/dL (7 mmol/L) more than once

• After 75 g oral glucose, diagnostic values are ≥ 200 mg/dL (11.1 mmol/L) 2 h after the oral glucose

• Hemoglobin A_1c (HbA_1c) ≥ 6.5%

• Often associated with hypertension, dyslipidemia, and atherosclerosis

General Considerations

• Due to nonimmune causes of pancreatic B-cell loss with variable degree of tissue insensitivity to insulin, that is, insulin resistance

• The residual beta cell function is sufficient to prevent ketoacidosis but is inadequate to prevent the hyperglycemia

• Strong genetic influences

• Prevalence of obesity in type 2 diabetes mellitus

  • 30% in Chinese and Japanese

  • 60–70% in North Americans, Europeans, and Africans

  • Nearly 100% in Pima Indians and Pacific Islanders from Nauru or Samoa

• Abdominal fat, with an abnormally high waist–hip ratio, is generally associated with obesity in type 2 diabetes. This visceral obesity correlates with insulin resistance, whereas subcutaneous fat seems to have less of an association

Demographics

• ~28 million Americans have type 2 diabetes

• Traditionally occurred in middle-aged adults but now more frequently encountered in children and adolescents

• No gender predominance

Clinical Findings

Symptoms and Signs

• Polyuria

• Increased thirst (polydipsia)

• Weakness or fatigue

• Recurrent blurred vision

• Vulvovaginitis or anogenital pruritus or balanoposthitis

• Peripheral neuropathy

• Obesity

• Often asymptomatic

Differential Diagnosis

Hyperglycemia

• Endocrinopathies

  • Type 1 diabetes mellitus

  • Cushing syndrome

  • Acromegaly

  • Pheochromocytoma

  • Glucagonoma

  • Somatostatinoma

• Medications

  • High-dose corticosteroids

  • Thiazides

  • Phenytoin

  • Niacin

  • Oral contraceptives

  • Pentamidine

• Pancreatic insufficiency

  • Subtotal pancreatectomy

  • Chronic pancreatitis

  • Hemochromatosis ("bronze diabetes")

  • Hemosiderosis

• Other

  • Gestational diabetes

  • Cirrhosis

  • Schmidt syndrome (polyglandular failure: Addison disease, autoimmune thyroiditis, diabetes)

Polyuria

• Diabetes insipidus

Hypercalcemia

• Psychogenic polydipsia

Nondiabetic glycosuria (benign)

• Genetic

• Fanconi syndrome

• Chronic kidney disease

• Pregnancy

Diagnosis

Laboratory Tests

• Fasting plasma glucose ≥ 126 mg/dL (7 mmol/L) or ≥ 200 mg/dL (11.1 mmol/L) 2 h after glucose load (Table 27–3)

• HbA_1c of at least 6.5%; reflects glycemic control over preceding 8–12 weeks

• Urine glucose (Clinistix, Diastix)

• Ketonuria on occasion without ketonemia (Acetest, Ketostix)

• Serum fructosamine

  • Reflects glycemic control over preceding 2 weeks

  • Helpful in the presence of abnormal hemoglobins and in ascertaining glycemic control at time of conception among diabetic women

• Lipoprotein abnormalities in obese persons with type 2 diabetes include

  • High serum triglyceride (300–400 mg/dL)

  • Low high-density lipoprotein (HDL) cholesterol (< 30 mg/dL)

  • A ...