Lecture 24: Diabetes Flashcards
Diabetes is not a single disease, what types of diabetes does it include?
Diabetes insipidus
Diabetes mellitus (insulin dependent and non insulin dependent)
Gestational diabetes
Bronze diabetes- occurring as a secondary effect in other diseases
What is diabetes?
A disorder of metabolism
What is bronze diabetes?
A form of diabetes which occurs as a secondary event in other diseases
Due to haemochromatosis which is a hereditary disease
Results in a combination of pigmented (bronze) skin and glucose intolerance
What are the early symptoms of diabetes?
Polydipsia, polyuria, blurred vision and extreme fatigue also occurs
What is diabetes insipidus?
Rare deficiency of ADH
ADH regulates reabsorption of water in the kidney.
Deficiency of ADH results in an inability to produce concentrated urine
This results in chronic water diuresis
What can diabetes insipidus be treated with?
Administration of ADH (vasopressin)
Which part of the brain does diabetes insipidus affect?
It is a disease of the posterior pituitary. (Cause unknown)
Although the cause of disease to the posterior pituitary is unknown, what are some hypothesised causes of diabetes insipidus?
Trauma or brain tumours which compress the adjacent pituitary gland
Sporadic/familial mutations in the vasopressin-neutrophin II gene
Mutations in the vasopressin receptor or transporter protein genes in the kidney
What is diabetes mellitus characterised by?
Fluctuations in blood glucose due to a deficiency in either insulin production or decreased effect of insulin.
What does fluctuations of blood glucose levels cause?
Hyperglycaemia
Fasting glucose >7.8mmol/L
2hour Postprandial glucose >11mmol/L
What does excessive glucose in the blood result in?
Hyperosmosis
What are body fluids with high sugar content diluted by?
Water from low sugar-containing body compartments
What does this dilution due to excessive blood glucose result in?
Dehydration of body tissues.
How is plasma volume maintained if excessive blood glucose is high?
Increased fluid excretion by the kidney (polyuria)
How is the excessive excretion of water and dehydration of tissues compensated by?
Increased thirst and hence increased fluid intake (polydipsia)
Why is blurred vision often the first sign of fluctuating glucose levels?
Because large variations in osmosis alter the curvature of the lens
What is type 1 DM.
Insulin dependent diabetes mellitus
Due to insufficient levels of insulin
Autoimmune disease trigger by something in the environment, but also evidence of genetic disposition
What is type 2 diabetes mellitus?
Non insulin dependent diabetes
Due to insufficient effect of insulin in peripheral tissues as well as insufficient insulin production in response to increased demand like a high energy diet
What happens to glucose normally after a meal?
Glucose is absorbed and delivered via the bloodstain to the liver.
Some blood also passes through the pancreas
Pancreas will detect high glucose in the blood and release insulin in response
The liver up takes and stores glucose as glycogen
Circulating levels of glucose are controlled from 10mM after a meal to 2mM within 2 hours
What happens when glucose levels are low (have been absorbed etc)
As glucose is used up peripherally this results in lowered blood sugar levels
The liver responds by converting glycogen to glucose
This is then released in the blood for body tissues to use
