33. Hyperglycemia and glucose-tolerance tests. Diagnosis of diabetes mellitus.

Hyperglycemia?

Defining is not straightforward

- As plasma glucose value varies depending on stress, recent food intake, circadian cycle and other factors

Why is the diagnosis of hyperglycemia important?

It is necessary for the diagnosis of any type of diabetes mellitus

Hyperglycemia?

Defining is not straightforward

- As plasma glucose value varies depending on stress, recent food intake, circadian cycle and other factors

Why is the diagnosis of hyperglycemia important?

It is necessary for the diagnosis of any type of diabetes mellitus

Alimentary hyperglycemia?

Is the hyperglycemia that occurs after a meal

The degree of which a food causes plasma glucose level to rise depends on?

Depends on the foods glycemic index

- Food containing easily absorbable mono-and-disaccharides (sucrose/fructose) - have a high glycemic index

= Causing plasma glucose to rise rapidly after meal

- Food containing complex carbohydrates & fibre have a lower glycemic index = causes less of a plasma glucose level spike after meal

Diet containing foods that have low glycemic index?

People with this diet have a lower risk for developing:

- DM type 2

- Coronary artery disease

- Obesity

Tools used to diagnose DM type 2?

Three tools, should ideally be used together:

- Fasting plasma glucose (FPG)

- Oral glucose tolerance test (OGTT)

- HbA1c

Fasting plasma glucose ranges?

Healthy: 3,5-6 mmol/L

Prediabetes: 6.0-7.0 mmol/L (impaired fasting glucose)

DM: > 7.0 mmol/L

Oral Glucose Tolerance test ranges?

Healthy: < 7.8 mmol/L

Prediabetes: 7.8-11.1 mmol/L (impaired OGTT)

DM: > 11.1 mmol/L

HbA1c - what is it?

Glycated hemoglobin

- Form of Hb that is covalently bound to glucose

- Formed from non-enzymatic glycation of Hb - is normal, also in healthy people

The level of HbA1c corresponds to the average plasma glucose level over 3 months (as RBCs only live 4 months)

HbA1c levels?

Healthy: < 5.7%

Prediabetes: 5.7-6.4%

DM: > 6.4%

Fasting plasma glucose - definition?

Going 12h without foods or sugary drinks

Normal, healthy range = 3,5 - 6,0 mmol/L

Oral glucose tolerance test (OGTT) - definiton?

An internationally standardized test - it tests the body's response to a glucose load

Procedure of OGTT?

1. Patient should eat normally in the days before the test

- Not be ill if possible

2. Fasting 12h before test

3. At physician's office: fasting Glc is taken

4. Patient is given oral solution containing 75g pure glucose that should be consumed within 5min (while sitting)

5. Blood may be drawn at 30-min intervals afterwards, but the most common: take plasma Glc sample after 2 hours

Patient with diabetes - reduced insulin response to high blood sugara?

Is either due to:

- Low levels of insulin

or

- Insulin resistance

= They will have a higher level of plasma glucose after a glucose load

When can the OGTT be false positive?

1. If the level of insulin-antagonist hormones is high, like:

- Cortisol

- Adrenalin

2. If the patient consumes few carbohydrates the day before, as this temporarily reduces the insulin-producing capacity of ß-cells

What is HbA1c mainly used for?

To track the blood glucose control of diabetics, rather than to diagnose it

Diagnosis of diabetes mellitus?

Depending on whether the patient has symptoms or signs of diabetes or not

Common symptoms:

- Polydipsia

- Polyuria

- Blurry vision

- Weight loss

One or more of these symptoms + a single test of FPG, OGTT or HbA1c = enough to confirm diagnosis

People who regularly should be screened for diabetes?

- People who previously established impaired glucose tolerance or impaired fasting glucose

- Pregnant women, week 24-28

- People above 45 w/ BMI > 27

- Mothers of large new-borns

- People w/ metabolic syndrome

- People whose close relatives have diabetes

= They should perform OGTT

What other findings may also rise suspicion for diabetes?

- Glucosuria

- Microalbuminuria

- Ketonuria

C-peptide?

Product of proinsulin cleavage

- Is usually produced in equal amounts as insulin

= May indicate which subtype of diabetes the person has

Decreased levels of C-peptide?

Indicate an absolute insulin deficiency & therefore type 1 diabetes

Increased levels of C-peptide?

Indicate hyperinsulinemia and therefore type 2 diabetes