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1. T2DM: an introduction

Professor Michael Nauck Professor Ele Ferrannini
Diabeteszentrum Bad Lauterberg Department of Internal Medicine
Bad Lauterberg im Harz, Germany University of Pisa School of Medicine
Pisa, Italy

What is T2DM?

Definition and diagnosis

Type 2 diabetes mellitus (T2DM) is a chronic, progressive disease, char-
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acterised by hyperglycaemia. Insulin resistance (i.e., a reduced cellular
response to the hormone) and impaired pancreatic β-cell function
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are the chief pathogenetic mechanisms. They often occur in concert,
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resulting in over-production of glucose from the liver, diminished glucose
uptake in tissues throughout the body, and consequently a net in-
crease in blood glucose levels.

Simple blood tests allow for the diagnosis of T2DM as well as predia-
betes, which is a condition of milder dysglycaemia at high risk of pro-
gressing to overt T2DM. The criteria for the diagnosis of prediabetes and
diabetes are presented in Table 1 and 2.

Table 1. WHO and ADA criteria for the diagnosis of prediabetes

Criteria for the diagnosis of prediabetes

Fasting plasma 110 to 125 mg/dL (6.1 mmol/l to 6.9 mmol/l) (WHO)
glucose (FPG) (4, 5) 100 to 125 mg/dL (5.6 mmol/l to 6.9 mmol/l) (ADA)
or

Post-prandial glucose 140 to 199 mg/dL (7.8 mmol/l to 11.0 mmol/l)
(PPG) a (5)
or

HbA 1c b (5) 5.7–6.4%

a Defined using the 2h oral glucose tolerance test (OGTT) after ingesting the 75g glucose load. 4
b The test should be performed in a laboratory using a method that is NGSP certified and
standardised to the DCCT assay. IFG and IGT represent intermediate states of abnormal
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glucose regulation that exist between normal glucose homeostasis and diabetes. Impaired
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fasting glucose (IFG) is now defined by an elevated fasting plasma glucose (FPG) concentration
(≥100 and <126 mg/dl; ≥5.6 and <7 mmol/l). Impaired glucose tolerance (IGT) is defined by an
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elevated 2-h plasma glucose concentration (≥140 and <200 mg/dl; ≥7.8 and <11.1 mmol/l)
after a 75-g glucose load on the oral glucose tolerance test (OGTT) in the presence of an FPG
concentration <126 mg/dl. 7 8
4