What is Diabetes Mellitus - Epidemiology Flashcards
Define diabetes mellitus
“A group of metabolic diseases of multiple aetiologies characterised by hyperglycaemia together with disturbances of carbohydrate, fat and protein metabolism resulting from defects in insulin secretion, insulin action, or both”
What are some symptoms of hyperglycaemia?
polydipsia - excessive thirst polyuria - excessive urination blurred vision weight loss infections
What are some microvascular complications associated with hyperglycaemia in diabetes?
retinopathy
neuropathy
nephropathy
What are some macrovascular complications associated with hyperglycaemia in diabetes?
stroke
MI
PVD
What are the diagnostic plasma glucose levels for diabetes?
Diagnostic glucose levels (venous plasma):
• Fasting ≥ 7.0 mmol/l
• Random ≥ 11.1 mmol/l
OGTT 2h after 75g CHO ≥ 11.1 mmol/l
What is the diagnostic plasma glucose level following an oral glucose tolerance test for diabetes?
OGTT 2h after 75g CHO ≥ 11.1 mmol/l
What is the diagnostic HbA1c level in plasma for diabetes?
Diagnostic HbA1c ≥ 48 mmol/mol.
What are the diagnostic plasma glucose and HbA1c levels for intermediate diabetes?
Impaired fasting glucose 6.1-7 mmol/l
Impaired glucose tolerance 2h glucose ≥7.8 and <11mmol/l
HbA1c 42-47mmol/mol
What is required for diagnosing diabetes?
ONE diagnostic lab glucose plus symptoms
TWO diagnostic lab glucose or HbA1c levels without symptoms
What is HbA1c?
Glycated haemoglobin
HbA1c is a measure of the beta-N-1-deoxy fructosyl component of hemoglobin
What is the clinical significance of HbA1c?
HbAic is a form of hemoglobin that is measured primarily to identify the three-month average plasma glucose concentration.
The test is limited to a three-month average because the lifespan of a red blood cell is four months (120 days). However, since RBCs do not all undergo lysis at the same time, HbA1C is taken as a limited measure of 3 months.
It is formed in a non-enzymatic glycation pathway by hemoglobin’s exposure to plasma glucose.
When can HbA1c levels not be used for diagnosing diabetes?
- All children and young people.
- Pregnancy—current or recent (< 2 months).
- Short duration of diabetes symptoms.
- Patients at high risk of diabetes who are acutely ill
- (HbA1c ‡ 48 mmol⁄ mol confirms pre-existing diabetes, but a value < 48 mmol ⁄ mol does not exclude it and such patients must be retested once the acute episode has resolved).
- Patients taking medication that may cause rapid glucose rise; for example, corticosteroids, antipsychotic drugs (2 months or less). HbA1c can be used in patients taking such medication long term (i.e. over 2 months) who are not clinically unwell.
- Acute pancreatic damage or pancreatic surgery.
- Renal failure.
- Human immunodeficiency virus (HIV) infection.
What medications can cause rapid increases in glucose levels?
Corticosteroids
Antipsychotics (only in first 2 months of taking it, after is fine to measure HbA1c)
What % of those with diabetes are type 1?
10.9%
What % of those with diabetes are type 2?
88.2%
What % of those with diabetes have other types of diabetes (aka not type 1 or 2)?
0.9%
If an individuals monozygotic twin has type 1 DM, what are the chances they have it as well?
30-50% concordance
If an individuals father has type 1 DM, what are the chances they have it as well?
6% risk
If an individuals mother has type 1 DM, what are the chances they have it as well?
1% risk
If an individuals sibling has type 1 DM, what are the chances they have it as well?
8% risk
If an individuals non-identical twin has type 1 DM, what are the chances they have it as well?
10% risk
If an individuals parents both have type 1 DM, what are the chances they have it as well?
30% risk
What is involved in the development of type 1 DM?
o Genetic pre-disposition plus
o Trigger e.g.? Viral infection
o Auto immunity
What are some symptoms and signs of type 2 DM?
Symptoms (may have none of the following): o Thirst o Tiredness o Polyuria / nocturia o Sometimes weight loss o Blurred vision o Symptoms of complications e.g. CVD
Signs:
o Not ketotic
o Usually overweight but not always
o Low grade infections, thrush / balanitis
o May have microvascular/macrovascular complications
What risk factors are used in screening tests for diabetes?
Risk factors—any two present
o Overweight
o Family history
o Over age 30 years if Maori ⁄ Asian (Indian subcontinent)⁄ Pacific Island descent
o Over age 40 years if European
o Previous history of diabetes in pregnancy
o Had a big baby (more than 4 kg)—not in immediate post-natal period
o Inactive lifestyle, lack of exercise
o Previous high blood glucose ⁄ impaired glucose tolerance
What other types of diabetes are there from type 1 and type 2 DM?
- Maturity onset Diabetes in the Young (MODY)
- Gestational diabetes
- Secondary diabetes
What is Maturity onset Diabetes in the Young?
Autosomal dominant
? 5% of people with diabetes
Impaired beta-cell function
Single gene defect, which results in either:
o Glucokinase mutations
o Transcription factor mutations (HNF-1a, HNF-1b, HNF-4a)
What % of people with diabetes have MODY?
5%
How do those with MODY that have a single gene defect in glucokinase differ to those with mutations in TFs?
Glucokinase mutations results in: o Onset at birth o Stable hyperglycaemia o Diet treatment o Complications rare
TF mutations: o Adolescence/young adult onset o Progressive hyperglycaemia o 1/3 diet, 1/3 OHA, 1/3 Insulin o Complications frequent
When do those with glucokinase mutations in MODY usually present, and what with?
o Onset at birth
o Stable hyperglycaemia
When do those with TF mutations in MODY usually present, and what with?
Adolescence/young adult onset
Progressive hyperglycaemia
How do you treat those with Glucokinase mutations in MODY?
Diet treatment
Complications rare
How do you treat those with TF mutations in MODY?
1/3 diet, 1/3 oral hypoglycaemic drugs (OHA), 1/3 Insulin
Complications frequent
What TFs are involved in MODY?
Hepatocyte nuclear factors:
HNF-1a, HNF-1b, HNF-4a
What can cause secondary diabetes mellitus?
Drug therapy e.g corticosteroids Pancreatic destruction • Haemochromatosis- excess iron deposition • Cystic fibrosis • Chronic pancreatitis • Pacreatectomy Recognised genetic syndromes - DIDMOAD Rare endocrine disorders e.g. Cushings syndrome, Acromegaly, Pheochromocytoma
What drug can cause secondary DM?
Corticosteroids
What can cause pancreatic destruction and result in secondary DM?
Haemochromatosis- excess iron deposition
Cystic fibrosis
Chronic pancreatitis
Pacreatectomy - removal of pancreas
What endocrine disorders can cause secondary diabetes?
Cushings syndrome - prolonged cortisol exposure
Acromegaly - increased GH from pituitary
Pheochromocytoma - tumour of adrenal gland
When does gestational diabetes usually present?
In 2nd or 3rd trimester
What neonatal problems are associated with gestational diabetes?
macrosomia (baby born big)
respiratory distress
neonatal hypoglycaemia
How much CHO is given in a OGTT, and how long after do you take a reading of plasma glucose?
75g CHO
1/2 hrs post feed
