LECTURE 10 (Diabetes) Flashcards
What is diabetes?
A chronic disorder characterised by increased blood glucose levels
CAUSES:
- insufficient insulin levels
- decreased response to insulin by the tissues
OR BOTH
SYMPTOMS:
- Polyuria (increased production or urine with frequent urination)
- Osmotic diuresis (increased urination due to glucose)
- Polydipsia (increased thirst and water intake)
- Blurred vision
- Weakness
- Slow healing of cuts/bruises
DIAGNOSIS:
- If patient is already symptomatic: Glucose level above 200mg/dl
- If patient is asymptomatic:
Fasting blood glucose level should be checked (no food for 8 hrs)
NORMAL - <100mg/dl
PRE-DIABETES - 100-125mg/dl
DIABETES - >125mg/dl
What does diabetes cause?
- Adult blindness
- Amputation
- Renal failure
- Nerve damage
- Heart attacks
- Strokes
What are the two types of Diabetes Mellitus?
- Type I (Insulin-dependent diabetes mellitus)
- Type 2 (Non-insulin-dependent diabetes mellitus)
What is the difference between Type I and Type 2 Diabetes Mellitus?
TYPE I
- body doesn’t make enough insulin
- most common in < 40 years old
- must take insulin
- glucose ONLY found in blood, no insulin
TYPE 2
- body doesn’t use insulin properly (insulin resistance)
- most common > 40 years old
- can take insulin + lifestyle changes
- insulin + glucose found in bloodstream
Why is it important to screen for diabetes?
Frequently there are no symptoms until complications develop
What is the Haemoglobin AIC test?
A test that can be used to diagnose diabetes. A small fraction of Haemoglobin A is “glycated” in humans (glucose combines with alpha or beta chains of haemoglobin) -> In diabetes, proportion of glaciated haemoglobin (haemoglobin AIC) level is increased
FINDINGS:
- Normal - <5.7%
- Pre-diabetes - 5.7% to 6.4%
- Diabetes - 6.5% or more
This test reflects average glucose level over the past 3 moths since lifetime of RBCs is 3 months -> very important for monitoring therapy (e.g high values reflect worse control of blood glucose levels)
Describe Type I DM
Type I DM is caused by autoimmune destruction of pancreatic beta cells by T-cells which secrete insulin -> Type 4 hypersensitivity reaction (T-cell mediated) -> Loss of ability to synthesise insulin and eventually its level drops to zero -> Lymphocytes can be seen on biopsy -> Associated with HLA-DR3 and HLA-DR4
PROPERTIES:
- Mostly a childhood disorder with two peaks (4-6 and 10-14 years)
- Often presents with symptoms of hyperglycaemia
TREATMENT:
- Insulin (2-3 daily injections of recombinant human insulin)
What are the stages of the development of Type I DM?
1) EXPOSURE TO A VIRUS/TOXIN may start the process of B-cell destruction in individuals with a genetic predisposition
2) Over the years, B-cells are destroyed which decreases production of insulin
3) When insulin secretory capacity falls below a threshold, symptoms of type I diabetes suddenly appear
What is Diabetic Ketoacidosis?
A life threatening complication of DM I and shows increased ketone levels due to the absence of insulin which induces acidosis (pH below 7.35)
SYMPTOMS:
- Fruity breath (from ketones)
- Dehydration (from polyuria)
- Abdominal pain, nausea and vomiting (decreased GI motility from acidosis)
- Increased levels of ketones in urine and blood
- Kussmaul breathing (deep, laboured breathing) -> hyperventilation to blow off CO2 and raise the pH (compensation for acidosis)
What are the properties of Diabetic Ketoacidosis?
- Occurs very rarely in type 2 (since some insulin present)
- Can be initial presentation of diabetes but can also occur when type I diabetes skips the insulin therapy
- Often precipitated by infection/trauma
What are the severe complications of Diabetic Ketoacidosis?
- Cerebral edema (brain swelling)
[common cause of death in patients] - Arrythmias
[occur due to hyperkalemia] - Mucormycosis
[fungal infection with RHIZOPUS/MUCOR SPECIES -> infection starts in sinuses and spreads to nearby structures -> thrives in high glucose environment -> FEVER, HEADACHE & EYE PAIN]
Describe the pathogenesis of Type II DM
Pancreas responds to increased blood glucose levels by increasing the secretion of insulin -> pancreas fails and insulin secretion decreases progressively -> can drop to zero if not treated
How is Obesity a major risk factor for Type II DM?
Central abdominal obesity carries the greatest risk -> Intra-abdominal (visceral) fat breakdown is less inhibited by insulin -> more LIPOLYSIS -> more FFAs -> used for fuel instead of glucose -> decreased glucose transport into cells -> weight loss improves glucose levels
Why is an “apple shape” worse than a “pear shape”?
Apple shape has increased visceral adipose tissue
Explanation: Increased visceral adipose tissue -> more lipolysis -> more FFAs -> used for fuel instead of glucose -> decreased glucose transport into cells
What are the risk factors for Type 2 DM?
- Being overweight
- Family history
- Lack of physical activity
- Being 45 or older
- Prediabetes
