Chapter 4: Endocrinology

DIABETES MELLITUS

Diabetes mellitus (DM) is an impairment in carbohydrate metabolism leading to hyperglycemia.

• Type 1 (juvenile diabetes): Due to absolute insulin insufficiency caused by destruction of pancreatic islet cells. Type 1 DM is typically autoimmune but can be idiopathic.

• Type 2 (most common type of DM and becoming more common in children): Due to insulin resistance and variable degrees of relative insulin deficiency.

• Gestational diabetes: A complication of pregnancy (see the Reproductive Health chapter).

• Other uncommon etiologies: Diabetes from pancreatic destruction (chronic pancreatitis, cystic fibrosis) and mature-onset diabetes of the young.

Symptoms/Exam

• May be asymptomatic (common in type 2 DM).

• Symptoms include polyuria, polydipsia, polyphagia, weight loss, blurry vision, acanthosis nigricans (a sign of insulin resistance; see Figure 4.1), dehydration, and neuropathy.

• Diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state are acute complications and can be the initial presentation of diabetes (see below).

Diagnosis

The American Diabetes Association diagnostic criteria for DM are as follows:

• Random plasma glucose concentration of ≥200 mg/dL combined with symptoms of diabetes.

• Plasma glucose of ≥126 mg/dL after 8 hours of fasting.

• Plasma glucose of ≥200 mg/dL 2 hours after a 75-g glucose load during an oral glucose tolerance test.

• A_1c ≥6.5%.

For all but the first criterion, you must repeat testing to confirm the diagnosis.

Screening

• The USPSTF recommends screening overweight or obese adults 40 to 70 years old (see the Community and Preventive Medicine chapter).

• Symptomatic individuals should be tested.

Management

• Glycemic control: Nonpharmacologic modalities are typically the first approach to glycemic control but pharmacologic agents are often added early in the disease course.

• Nonpharmacologic: Diet, exercise, weight loss, and stress management can all help control glucose levels and ↓ the need for other medications in type 2 DM.

• Pharmacologic:

  • First line: Metformin is used in diabetics without contraindications because it is the only oral agent shown to reduce mortality.

  • If control is not achieved with metformin plus 1 to 2 additional agents despite good adherence, patients should be changed to insulin. There is no evidence that newer agents are more effective than insulin.

  • Table 4.1 outlines medications for the treatment of type 2 DM.

  • Insulin is appropriate for type 1 and type 2 DM. Options include a “basal-bolus” regimen (basal coverage with intermediate- to long-acting insulin plus a short-acting bolus insulin ...