Diagnosis of Diabetes

Question 1

What is the definition of diabetes?

Answer 1

A metabolic disorder of multiple aetiology characterised by chronic hyperglycaemia with disturbance in carb/protein/fat metabolism resulting from defects in insulin secretion/action or both.

Question 2

What are the symptoms of diabetes?

Answer 2

• Polyuria,
• Nocturia,
• Thirst,
• Polydipsia,
• fatigue,
• Change in weight,
• Blurring of vision,
• Genital candidiasis,
• Nausea,
• Vomiting,
• Headache,
• Hyperphagia,
• Mood changes

Question 3

What is the diagnostic criteria for diabetes?

Answer 3

• Fasting glucose >7mmol/L,
• Random plasma glucose .11.1mmol/L,
• HbA1c .6.5% or 48mmol/mol.
• Either one abnormal value if symptomatic or two if asymptomatic

Question 4

What may cause a false low HbA1c and what may cause a false high HbA1c?

Answer 4

Low - Sickle cell anaemia or pregnancy (anything that shorted RBC lifespan)
High - Splenectomy or anything that increases red cell life span

Question 5

What are some different types of diabetes?

Answer 5

• Type 1 (Immune pathogenesis and severe insulin deficiency)
• Type 2 (combination of insulin resistance and deficiency)
• Gestational
• Genetic defects of beta cell function,
• Pancreatic disease and more

Question 6

Explain the pathophysiology of DKA

Answer 6

With absolute insulin deficiency there is increased lipolysis which increases free fatty acids and glycerol which increases ketogenesis which causes metabolic acidosis

Question 7

Explain the pathophysiology oh hyperosmolarity in diabetes

Answer 7

• With insulin deficiency there is increased glycogenolysis and gluconeogenesis which causes hyperglycaemia. This causes glycosuria, osmotic diuresis and dehydration which can cause hyperosmolarity.

Question 8

What is the best investigation for DKA?

Answer 8

Blood testing strips to detect beta hydroxybutyrate as ketonuria/ketonaemia can be found after exercising, repeated vomiting or eating a ketogenic diet.

Question 9

What do the following capillary ketone values suggest?
- <0.6mmol/L
- 0.6-1.5mmol/L
- 1.5-3.0mmol/L
- >3.0mmol/L

Answer 9

• <0.6mmol/L = normal
• 0.6-1.5mmol/L = metabolic control deteriorating
• 1.5-3.0mmol/L = high risk of DKA, seek medical advice.
• > 3.0mmol/L = suggests DKA

Question 10

What is the difference between hyperosmolar hyperglycaemic state and DKA?

Answer 10

HHS - Type 2 diabetes, older age, duration of onset is days to weeks, abdo pain uncommon, more volume depleted and relative insulin deficiency.
DKA - Type 1 diabetes, younger age, presetns within hours to days, abdo pain is common and they have absolute insulin def

Question 11

What is the definition of DKA?

Answer 11

• Hyperglycaemia and hyperketonaemia/ketonura 2+ and metabolic acidosis (bicarb <15 or pH <7.3)

Question 12

What is the definition of hyperosmolar hyperglycaemia state

Answer 12

• Hyperglycaemia (usually >30mmol/L) and hyperosmolality ( >320mOsm/kg) without significant ketonaemia/ketoneuria or metabolic acidosis

Question 13

What is the pathogenesis of type 1 diabetes

Answer 13

• Autoimmune destruction of insulin producing beta cells in islets of Langerhans.
• Genetic susceptibility + environmental trigger (viral infection, diet/diet toxin, vitamin D def or immune checkpoint inhibitors)

Question 14

What are the autoimmune markers associated with T1DM?

Answer 14

• Anti-GAD,
• Anti-IA-2,
• Anti-ZnT8

Question 15

What is a useful marker of endogenous insulin secretion?

Answer 15

C-peptide as it is cleaved from pro-insulin to form insulin. Useful as it is not a constituent of synthetic insulin.
- can be measured in blood or urine but needs paired blood glucose.
- <200mmol/L is seen in T1D, pancreatic diabetes and MODY. Shows severe insulin deficiency.
- >900mmol/L due to increased insulin because of resistance so seen in T2.

Question 16

Compare type 1 and type 2 diabetes

Answer 16

Type 1 - Age of onset under 40, family history of diabetes is less common, autoimmune disease, ketoacidosis is common, c peptide is less than 200 and autoantibodies are +ve, other autoimmune diseases are common.
Type 2 - Age onset over 50, usually overweight, family history is more common, ketoacidosis is uncommon, there is partial insulin def but resistance, C peptide is usually over 900 and negative for autoantibodies

Question 17

Describe features of pancreatic diabetes

Answer 17

• Can be caused by pancreactectomy, pancreatitis, haemochromatosis, carcinoma or CF.
• Higher risk of hypos than in T1D due to loss of alpha cells that produce glucagon,
• May have ketones and acidosis,
• C peptide is low/undetectable,
• Pancreatic autoantibodies are negative,
• Treat with SU and insulin

Question 18

What is MODY?

Answer 18

Maturity onset diabetes of the young. It is an autosomal dominant mutation in HNF1-A that presents under age 25. Managed by diet, sulphonylureas or insulin