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Diabetes Mellitus Type 2Published by: Domus Medica | SSMGLast published: 2017Diabète sucré de type 2Published by: SSMG | Domus MedicaLast published: 2017

Key diagnostic factors

common

It is very common for type 2 diabetes to be asymptomatic and detected on screening. Symptoms, when present, may indicate more overt hyperglycemia.

Usually in patients with fasting plasma glucose >300 mg/dL (>16.7 mmol/L), HbA1c >11% (>97 mmol/mol).

Usually in patients with fasting plasma glucose >300 mg/dL (>16.7 mmol/L), HbA1c >11% (>97 mmol/mol).

If marked hyperglycemia is present.

Usually in patients with fasting plasma glucose >300 mg/dL (>16.7 mmol/L), HbA1c >11% (>97 mmol/mol).

uncommon

Diabetic ketoacidosis and hyperosmolar hyperglycemic state may be the initial presentation of type 2 diabetes, particularly in ethnic and racial minorities, or if there is an underlying infection.[2]​​[3]​​​ Patients are symptomatic of hyperglycemia (polyuria, polydipsia, weakness) and significant volume depletion (dry mucous membranes, poor skin turgor, tachycardia, hypotension, and, in severe cases, shock). This is a life-threatening emergency and requires early diagnosis and management.[81] 

Other diagnostic factors

common

Increased fatigability may be an early warning sign of progressive cardiovascular disease; clinicians should have a low threshold for cardiac evaluation.

Due to elevated glucose.

Due to glucose-induced diuresis.

Most commonly vaginal, penile, or in skin folds.

Cellulitis or abscesses.

Cystitis or pyelonephritis.

uncommon

May occur in the extremities as a result of neuropathy in those with prolonged undiagnosed diabetes.

A velvety, light brown-to-black marking, usually on the neck, under the arms, or in the groin. Can occur at any age. Most often associated with obesity-related hyperinsulinemia. [Figure caption and citation for the preceding image starts]: Acanthosis nigricans involving the axillaFrom the collection of Melvin Chiu, MD; used with permission [Citation ends].com.bmj.content.model.Caption@20cda8d1

Risk factors

strong

Although not present in all older adults, insulin resistance and reducing beta-cell function appear to be associated with aging.[25]​ Older patients are at increased risk of type 2 diabetes, with the incidence peaking between 70 and 79 years.[29] However, the incidence of type 2 diabetes in children and adolescents is increasing.[30] The American Diabetes Association recommends, in the absence of other risk factors, that screening should begin for all people at age 35 years.[2]

Appears to be the precipitating factor leading to clinical expression of diabetes.[31][32]​​​​ There is a graded increase in risk of diabetes with increasing body mass index (BMI).[33]​ A larger waist circumference, independent of overall adiposity, is strongly and linearly associated with increased risk.[34] Clinical trials have shown that weight loss is associated with delayed or decreased onset of diabetes in high-risk adults.[35][36]​​​[37][38]​​ For adults at any age, screening should be considered if BMI is ≥25 kg/m² (≥23 kg/m² for Asian-Americans), in the presence of at least one other risk factor.[2] The threshold is lower for Asian-Americans than other ethnicities as data indicate a higher risk in this population at lower BMIs.[2][11]

Gestational diabetes mellitus affects 4% to 10% of pregnancies worldwide.[39] Women with a history of gestational diabetes have an increased lifetime maternal risk for diabetes estimated at 50% to 60% and a 10-fold increased risk of developing type 2 diabetes compared with those without gestational diabetes.[2][40]​​ Gestational glucose intolerance, which includes conditions not meeting gestational diabetes criteria, has also been found to confer a high risk of type 2 diabetes in young adulthood.[41] Up to one third of individuals with gestational diabetes will be diagnosed with diabetes or impaired glucose metabolism within 12 weeks after delivery.[42]​ Lifelong screening for diabetes at least every 3 years is recommended in women with a history of gestational diabetes.[2]​ Risk factors for progression from gestational diabetes mellitus to type 2 diabetes include pregnancy-specific (hypertensive disorders of pregnancy, preterm delivery, and early gestational age at onset of gestational diabetes mellitus [though the latter could reflect early detection of preexisting dysglycemia]) and generic risk factors for diabetes (raised body mass index, nonwhite ethnicity, and family history of diabetes).[39]

Is defined by a single fasting plasma glucose of 100-125 mg/dL (5.6-6.9 mmol/L), or plasma glucose of 140-199 mg/dL (7.8-11.0 mmol/L) 2 hours after 75 g oral glucose, or an HbA1c of 5.7% to 6.4% (39-47 mmol/mol) in the absence of diabetes, and is a major risk factor for onset of type 2 diabetes.[2] In the US, 97 million people ages 18 years or older have prediabetes (38% of the adult population) and the prevalence is increasing.[43][44]​​ Progression from prediabetes to overt type 2 diabetes occurs at the rate of about 2% to 4% per year.[1] Annual screening for type 2 diabetes is recommended for people with prediabetes.[2] 

Although the specific genetic profile that confers risk has yet to be fully elucidated, epidemiological observations leave little doubt of a substantial genetic component.[5]

Relative to white people, National Health and Nutrition Examination Survey (NHANES) and other data demonstrate higher risk of diabetes.[11]​​[45]​​

While the impact of physical inactivity on increased risk of diabetes is mediated in part through an increased likelihood of having obesity/overweight, reduced levels of physical activity also seem to be an independent risk factor for developing type 2 diabetes. In people with or at risk for developing type 2 diabetes, extended sedentary time is associated with poorer glycemic control and clustered metabolic risk.[2] Increased levels of physical activity have been shown to delay or decrease onset of diabetes in high-risk adults.[36][46]​​

One of the most common endocrine disorders in women of reproductive age, with a global prevalence between 7% and 12%.[39] Associated with elevated risk of type 2 diabetes; testing for diabetes should be considered in women with overweight or obesity (BMI ≥25 kg/m² or ≥23 kg/m² in Asian-Americans) with PCOS.[2]​ Risk factors for progression to type 2 diabetes mirror those generic factors seen in gestational diabetes mellitus (e.g., high body mass index, family history of type 2 diabetes, nonwhite ethnicity) but might also include factors specific to PCOS such as hyperandrogenism.[39]

Often associated with type 2 diabetes. Testing for diabetes should be considered in adults with overweight or obesity (BMI ≥25 kg/m² or ≥23 kg/m² in Asian-Americans) whose blood pressure is ≥130/80 mmHg or who are on therapy for hypertension.[2]

Especially with low HDL (<35 mg/dL [0.9 mmol/L]) and/or high triglycerides (>250 mg/dL [2.82 mmol/L]). Testing should be considered in adults with overweight or obesity (BMI ≥25 kg/m² or ≥23 kg/m² in Asian-Americans) whose HDL cholesterol level is <35 mg/dL (0.9 mmol/L) and/or who have a triglyceride level >250 mg/dL (2.82 mmol/L).[2]

Comorbidities including hypertension and dyslipidemia are common to both cardiovascular disease and type 2 diabetes.[2] Testing for diabetes should be considered in adults with overweight or obesity (BMI ≥25 kg/m² or ≥23 kg/m² in Asian-Americans) who have a history of cardiovascular disease.[2]

Stress provokes release of hormones that elevate glucose, and there is some evidence that life stress may predispose to onset of type 2 diabetes.[47][48]​​

According to the World Health Organization, there is increasing evidence from clinical and epidemiologic studies highlighting the role of tobacco in the development and exacerbation of type 2 diabetes and diabetes-related health complications.[49]​ Research indicates that nicotine impairs the function and mass of pancreatic beta cells, which in turn affects the production of insulin and regulation of glucose production.[50][51]​​​​ There is also evidence to suggest that nicotine induces insulin resistance through activation of oxidative stress.[52][53]​​​ Passive smoking also seems to increase risk of type 2 diabetes.[54]

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