Diabetes mellitus

Question 1

Describe the WHO classification of:

1. Diabetes mellitus
2. Impaired glucose tolerance
3. Impaired fasting glycaemia

Answer 1

1. Diabetes mellitus - a metabolic disorder of multiple causes characterized by chronic hyperglycaemia resulting from defects in insulin secretion, insulin action or both
2. Impaired glucose tolerance (IGT) is a pre-diabetic state of hyperglycemia that is associated with insulin resistance and increased risk of cardiovascular pathology.
3. Impaired Fasting Glycaemia is a type of prediabetes, in which the blood sugar level during fasting is consistently higher than what are considered normal levels; however, the level is not high enough to be diagnosed as diabetes mellitus. This pre-diabetic state is associated with insulin resistance and increased risk of cardiovascular pathology, although of lesser risk than impaired glucose tolerance (IGT). Patients identified to have IFG should undergo the 2hr glucose test to rule out IGT.

Question 2

What are the blood gluose values for normal, diabetes, impaired glucose intolerance and impaired fasting glucose?

Answer 2

Normal

• Fasting: <6.1
• 2hr after 75g glucose: <7.8

Impaired fasting glycaemia

• Fasting: >6.1
• 2hr after 75g glucose: n/a

Impaired glucose tolerance

• Fasting: 6.1-7.0
• 2hr after 75g glucose: 7.8-11.1

Diabetes Mellitus

• Fasting: >7.0
• 2hr after 75g glucose: 11.1

Question 3

Classify the major types of diabetes mellitus

Answer 3

Type I DM:

• Autoimmune disease, with autoantibodies targeted against the insulin-secreting ß cells of the Islets of Langerhans in the pancreas, leading to cell death and inadequate insulin secretion
• It is hypothesised that viral infection

Type II DM:

• Unlike type I diabetes, blood insulin levels are initially normal, or even increased in the early stages to compensate for insensitivity of the bodily tissues to the insulin
• The ‘insulin resistance’ is associated with aging, genetic factors, obesity, high fat diets and a sedentary lifestyle
• Eventually the ß cells decompensate, and can no longer produce excess insulin, leading to hyperglycaemia

Gestational Diabetes Mellitus

• may occur during pregnancy. It results in a similar hyperglycaemia, of variable severity, recognised first during pregnancy. Impaired glucose control may antedate pregnancy.
• Capillary glucose levels for impaired glucose tolerance are used for diagnosis with clinical symptoms.

Maturity Onset Diabetes of the Young (MODY)

• may represent 5-10% of diabetic patients.
• This form of diabetes is clinically similar to T2DM but presents in young patients

Question 4

What are the secondary causes for 1% cases of diabetes?

Answer 4

• Pancreatic disease:
  
  • CF, chronic pancreatitis, pancreatic carcinoma
• Endocrine disease:
  
  • Cushing’s disease, acromegaly, thyrotoxicosis, PCC, glucagonoma
• Drug induced:
  
  • Thiazide diuretics, corticosteroids, antipsychotics, antiretrovirals
• Congential disease:
  
  • Insulin receptor abnormalities, myotonic dystrophy, Friedreich’s ataxia

Question 5

What are the typical presentations of a patient with Type I DM?

Answer 5

• Presents in childhood/aldolescence with a 2-6 week history of;
  
  • Polyuria: high sugar content in urine leading to osmotic diuresis
  • Polydipsia: due to resulting fluid loss
  • Weight loss: fluid depletion plus fat/muscle breakdown
• Diabetic Ketoacidosis (DKA) is also a common first presentation

Question 6

What are the typical presentations of a patient with Type II DM?

(compare and contrast with type I DM)

Answer 6

• The clinical onset may be over many months/years, with the classic triad of symptoms present, but less obvious than in type I DM
• More common presenting features are:
  
  • Lack of energy
  • Visual blurring: glucose-induced refractive changes
  • Pruritis vulvae/balantitis: due to candida infection
• In older patients, it may be the complications of diabetes that are the presenting feature:
  
  • Retinopathy: noted by the optician
  • Polyneuropathy: tingling and numbness in the feet
  • Erectile dysfunction
  • Arterial disease: MI/peripheral vascular disease
• Type II DM is recognised as part of the metalbolic syndrome:
  
  • T2DM
  • Central obesity
  • Dyslipidaemia: low HDL cholesterol, hypertriglyceridaemia

Question 7

List the clinical features of type I diabetes mellitus

Answer 7

• Ketoacidosis
• younger patient
• polyuria
• polydipsia
• weight loss
• onset over weeks.

Question 8

What are the priciples of the dietary treatment of type 1 and type 2 diabetes?

Answer 8

Diet: no different to that considered healthy for everyone:

• High in low-GI carbohydrates
• Limit foods high in sugar and saturated fats
• Diabetic specific foods are not required
• Can see nutritionist to help with meal plans
• Allowed alchol but may exacerbate/prolong effect of hypoglycaemic drugs and may make the signs of hypo less clear

Toms guide:

Protein – 1g/kg Fat - <35% total intake. Keep sat+trans fat<10% of total intake. CHO – 40-60% of total intake. Choose low GI foods. Fruit, vegetables, some alcohol allowed. Salt < 6g Recommend fibre. Salt <6g a day (<3g a day in hypertensive diabetic patients)

Question 9

Describe the methods of evaluating diabetic control

Answer 9

Urine testing;​

• Urine tests using dipsticks give patients who do not use blood testing some idea of how well controlled their glucose levels are. However, the relationship between urine glucose levels and blood glucose levels is not exact, for 3 main reasons:

1. changes in urine glucose lag behind blood changes
2. the mean renal threshold is 10mM, but the range is wide
3. urine tests can give no guidance concerning glucose levels below the renal threshold (hypos go unchecked)

Home blood glucose testing

• Home blood glucose testing is the best place for assessment of day-to-day control, and is an essential aid to that control.
• Patients are able to control their insulin dose appropriately.
• Patients should generate a profile, for example: 4 tests aday, 2 days a week; and share this with nurses to help enable the best system available for them to be used.

HbA1c:

• HbA1c is generated as a two step reaction eventually resulting in glucose attaching to the valine in the Beta chain of a Hb molecule.
• The rate at which this occurs depends on glucose concentrations. Normal range is between 4-6.2% (<48). This gives us an idea of control of blood glucose levels over the lifespan of Hb, about 6 weeks.
• Should be checked 6 monthly
• The figure will be misleading in anaemia, thalassaemia, haemoglobinopathy or pregnancy, in which case the shorter-term fructosamine test may be used.