Endocrine Flashcards
Define diabetes
A disorder of carbohydrate metabolism characterised by chronic hyperglycemia due to relative insulin deficiency (type 1) or insulin resistance (type 2)
What is the principal organ of glucose homeostasis
Liver
Normal physiological response when need to increase blood glucose (2 processes)
Glycogenolysis
Gluconeogenesis
Controlled by glucagon
Main insulin independent tissue
Brain
Why is brain the major consumer of glucose
Brain function is dependent on a continuous supply as it cannot use free fatty acids for energy as they cannot cross the blood brain barrier
Normal physiological process after feeding
Increase in blood glucose 5-10 mins after feeding stimulates insulin secretion and suppresses glucagon
60% of ingested glucose goes to the periphery (muscle) to replenish the glucose store
40% of ingested glucose goes to the liver - glycogenesis
Roles of insulin
Decrease hepatic glucose output
Increase glucose uptake into insulin sensitive tissues
Suppresses lipolysis and decreases ketogenesis
Physiology of insulin secretion by the beta cell
- GLUT-2 glucose transporter has a low affinity for glucose. Glucose flows freely into the beta cell
- Glucose is phosphorylated by glucokinase
- Increase rate of ATP formation from ADP
- Increased ATP concentration closes the K+ channels
- Change in membrane polarity
- Voltage gated Ca2+ channels open and Ca2+ ions enter the cell
- Increased concentration of Ca2+ causes insulin vesicles to move to the outer cell membrane
- Insulin is secreted
What form is insulin secreted in
Insulin is secreted as proinsulin. Alpha and beta chains are joined together by C peptide. Once proinsulin is secreted C peptide is cleaved off
What is biphasic insulin release
First rate response = rapid as it is the release of stored insulin
Second rate response = slower release of newly synthesised insulin
What is the action of insulin in muscle and fat cells
- Insulin binds to insulin receptor on the muscle/fat cell
- The binding activates tyrosine kinase which triggers an intracellular signalling cascade
- Insulin mobilises GLUT-4 vesicles in the cell which migrate to the plasma membrane
- GLUT-4 vesicles are integrated into the plasma membrane
- GLUT-4 vesicles allow glucose to enter the cell
How can you increase GLUT-4 receptors
The more glucose there is the more GLUT-4 receptors there are
How can you increase insulin sensitivity
Exercise can increase insulin sensitivity
What is type 1 diabetes
Inadequate insulin production and secretion by the beta cells of the pancreas caused by autoimmune destruction
Epidemiology of type 1 diabetes
Typically is adolescent presentation
Lean patient
Increase prevalence in those of N.European ancestry
Risk factors for type 1 diabetes
Northern European (esp Finnish)
Family history
Genes : HLA-DR3 and HLA-D4
Other autoimmune diseases (i.e Grave’s, coeliac)
Pathogenesis of type 1 diabetes
Type IV hypersensitivity reaction as T cells attack the pancreatic beta cells due to their loss of self tolerance
Destruction of the beta cells causes insulin deficiency as it is not secreted by the cells.
Autoantibody formation against islet beta cells
Consequences of the failure of insulin secretion
No insulin leads to…
1. No insulin effect on muscle / fat –> impaired glucose clearance and muscle increased muscle/fat breakdown –> less glucose enters the peripheral tissue
2. No hepatic insulin effect –> unrestricted production of glucose and ketones –> more glucose enters the blood
Leads to hyperglycaemia and increase in plasma ketones
Glycosuria and ketonuria
How many beta cells are typically destroyed at the time symptoms develop in type 1 diabetes
90%
What would happen if you didn’t treat type 1 diabetes with insulin
Increased concentration of glucagon in the circulation (due to the loss of local insulin within the islets there is no negative feedback and inhibition of glucagon release)
State of perceived stress leads to increased cortisol and adrenaline
Progressive catabolic state leads to increased ketones
Clinical presentation of type 1 diabetes (symptoms)
Polyuria and nocturia Polydipsia Unexplained weight loss Usually an acute presentation of a young person 2-6 week history
Why polyuria and nocturia in presentation?
Not enough glucose can be reabsorbed by the kidneys as they have reached the renal threshold for maximum resorptive capacity
Increased glucose in the tubule so less water being reabsorbed by osmosis
Increased urine output
Why polydipsia in presentation?
Due to loss of electrolytes and fluid in urine
Why is there weight loss in type 1 diabetes presentation
Due to fluid depletion and accelerated breakdown of fat and muscle secondary to insulin deficiency
Catabolic state - loss of muscle
Hunger
Signs of type 1 diabetes
Glycosuria
Ketonuria
Patient’s breath may smell like pears (ketones)
Complications as the presenting complaint (type 2)
Staphylococcal skin infection
Retinopathy
Neuropathy
Erectile dysfunction
What investigations would you do in someone with suspected diabetes
Random plasma glucose
Fasting plasma glucose
Oral glucose tolerance test
HbA1c
What is the oral glucose tolerance test
Patient fasts for 8-12 hours before you take their blood
Give 75mg of glucose and test blood two hours later
What is HbA1c
Measures of the amount of glycerated haemoglobin
It assess the blood glucose level over the past few months (120 days ~ RBC lifespan)
Other tests in your investigation for patients with diabetes that does not include looking at blood glucose levels ?
FBC
U&Es
Screen urine for microalbuminuria to assess for kidney disease
blood pH to look for ketoacidosis
What is diagnostic for random plasma glucose
11.1mmol/L or more
What is diagnostic for fasting plasma glucose
7.0 mmol/L or more
What is diagnostic for HbA1c
48 or more
6.5% or more
What do you need to diagnose diabetes
Abnormal HbA1c
One abnormal random or fasting plasma glucose + symptoms
Two abnormal results for random and fasting plasma glucose if asymptomatic
Principles of treatment of diabetes (type 1 and 2)
- control of symptoms
- prevention of acute emergencies
- identification and prevention of long-term microvascular complications
- Patient education on their disease and risks
- Maintain a lean weight, don’t smoke and take care of feet
What is the treatment for type 1 diabetes
insulin
How is insulin administered
subcutaneous injection into the abdomen (fastest absorption rate)
How is insulin activated
GI enzymes
What factors can change insulin absorption
local tissue reactions
changes in insulin sensitivity
injection site
blood flow
why is it important to change up the injection site for insulin
to prevent lipohypertrophy (fatty lumps)
what are the three groups of insulins
short-acting insulin
intermediate acting insulin
long acting insulin
What is the first line choice treatment for an insulin regime
multiple daily injection basal-bolus insulin
one or more separate daily injections of intermediate acting insulin or long-acting insulin analogue as the basal insulin
alongside multiple bolus injections of short acting insulin before meals
what is the biphasic regime
1,2 or 3 insulin injections per day of short acting insulin mixed with intermediate-acting insulin
what is continuous insulin infusion
insulin pump
regular or continuous amount of insulin (usually rapid-acting insulin analogue or soluble insulin) delivered by a programmable pump and insulin storage reservoir via a subcutaneous needle
symptoms of hypoglycaemia
hungry sweating tingling lips tremor weakness blurred vision easily irritable
complications of insulin therapy
hypoglycaemia
insulin resistance - mild
lipohypertrophy
weight gain
define type 2 diabetes
caused by decreased insulin resistance with or without decreased insulin secretion
Epidemiology of type 2 diabetes
common in all populations enjoying an affluent lifestyle
Increasing incidence due to ageing population and increasing obesity in the west
older patients over 40 yrs old
Increased prevalence in men
More prevalent in south asian, african and caribbean ancestry
Risk factors for type 2 diabetes
family history - first degree relatives. There is a stronger genetic link in type 2 diabetes than type 1 Increasing age obesity sedentary lifestyle ethnicity pmh gestational diabetes pmh of heart disease or stroke high waist circumference hypertension low level of HDL cholesterol smoking excessive alcohol consumption
pathogenesis of type 2 diabetes
- insulin dependent cells do not respond to insulin (resistance - post receptor)
- excess adipose tissue releases FFA that can cause inflammation and influence cell resistance
- beta cells undergo hyperplasia and hypertrophy to increase insulin secretion
- beta cells secrete amyloid polypeptide and amylin
- amylin builds up and aggregates in the islets leading to amyloid deposits in the beta cells
- beta cells become dysfunctional and undergo hypoplasia and hypotrophy
- impaired insulin secretion
- hepatic insulin resistance –> excessive glucose production –> more glucose enters bloodstream
- muscle / fat insulin resistance –> decreased glucose uptake after a meal –> impaired glucose clearance and less glucose enters peripheral tissues
- hyperglycaemia
- glycosuria
what is impaired glucose tolerance
HbA1c of 42-47 mmol/L
A unique window for lifestyle intervention
clinical presentation of type 2 diabetes
overweight increased visceral fat polydipsia polyuria weight loss usually a subacute presentation and onset is over several months or years
why is ketoacidosis rare in type 2
low insulin levels are sufficient to suppress catabolism and prevent ketogenesis
investigations of type 2 diabetes
same tests as type 1
older patients may present with established complications - retinopathy
patients with severe insulin resistance may have acanthosis nigricans (blackish pigmentation at the nape of the neck and axillae)
Objectives of treatment of type 2
manage blood glucose
reduce risk of: CVD mortality and morbidity, CKD, microvascular complications
Weight reduction : increase physical activity and decrease dietary fats
progression of treatment in type 2 diabetes
Lifestyle metformin dual therapy triple therapy insulin
lifestyle interventions and advice for type 2 diabetes patients
community run lifestyle education programmes e.g DESMOND
Moderately rigorous activity for up to 30 minutes a day
Reduce portion sizes
Diet : low carbohydrate diets, low sugar with high in starch carbohydrates with a low glycaemic index
Stop smoking
Control of blood pressure e.g with ramipril
Hyperlipidaemia control e.g statins
Can give orlistat in obesity (intestinal lipase inhibitor) that reduces absorption of fat from the diet
What is second line therapy for type 2 diabetes
metformin
what type of drug is metformin
biguanide drug
mechanism of metformin
oral drug that works by preventing the production of glucose in the liver, improving the body’s sensitivity towards insulin and reducing the amount of sugar absorbed by the intestines
what does metformin do
reduces the rate of gluconeogenesis in the liver
increases cells sensitivity to insulin
weight loss promotion
reduces CVD risk in diabetes
Side effects of metformin
anorexia
diarrhoea
nausea
abdominal pain
What drugs can we use as second line dual therapy?
sulfonylurea
pioglitazone
incretin based agents (GLP-1 receptor agonist, DPP-4 inhibitors)
SGLT-2 inhibitor
what is the mechanism of sulfonylurea
pushes the beta cells in the pancreas to produce more insulin
rapid improvement in glycaemic control
cons to using sulfonylurea
overtime it loses its effectiveness (6-8 years)
causes weight gain initially
example of a sulfonylurea
gliclazide
what are incretins
hormones secreted by intestinal endocrine cells in response to nutrient intake
they influence glucose homeostasis by: glucose-dependent insulin secretion, postprandial glucagon suppression and slowing of gastric emptying
What is the effect of GLP-1 in humans
glucose enters gut
GLP-1 hormone is released which increases insulin production and promotes satiety, decreasing appetite
Lowers blood sugars
Broken down by DPP-4
example of a GLP-1 receptor agonist
exenatide
mechanism of a GLP-1 receptor agonist
increases GLP-1 levels
induces a delay in gastric emptying
benefit of a GLP-1 receptor agonist
induces weight loss by 3-4 kg
who can start on GLP-1 receptor agnoists
patient has to have a BMI greater than 35
example of a DPP-4 inhibitor
sitagliptin
what do DPP-4 inhibitors do
small increase in endogenous GLP-1
example of an SGLT-2 inhibitor
empagliflozin
mechanism of SGLT-2 inhibitors
works on the kidneys by reducing the resorption of glucose in the kidneys at the PCT
increases renal excretion of glucose and decreases blood glucose
when do we use SGLT-2 inhibitors
these are increasingly being used as second line treatment for dual therapy after metformin
complications of SGLT-2 inhibitors
GU infections due to increased glycosuria
affect women more than men
easily managed and patients need to be reassured about continuing the treatment
side effect of SGLT-2 inhibitors
may cause intravascular volume depletion
need to monitor patients for symptoms of hypotension
mechanism of action of pioglitazone
increases insulin sensitivity
side effects of pioglitazone
hypoglycaemia
fractures
fluid retention
can increase weight
contraindications of using pioglitazone
congestive heart failure
osteoporosis
macula oedema
risks of developing diabetic retinopathy
long duration of diabetes poor glycaemic control hypertensive on insulin pregnant
what is an effective way of preventing patients developing early diabetic retinopathy
eye screening
anyone over the age of 11 with diabetes
photographs are taken and graded
pathogenesis of diabetic retinopathy
- hyperglycaemia triggers apoptosis of pericytes
- causes localised outpouching of capillary walls
- microaneurysms form
- microaneurysm formation + smooth muscle cell loss can lead to leakages
- breach of microaneurysm causes fluid to leak into the retina
- fluid is cleared by the retinal veins and leaves behind protein and lipid deposits
- retina compensates for loss of cells by growing new glial cells in capillaries
- leads to occlusion
- pericyte loss causes endothelial cells to increase turnover which can cause thickening (ischaemia)
- ischaemia leads to release of vascular growth factors that cause new blood vessels to grow which are prone to haemorrhaging
how can you see evidence of diabetic retinopathy on a photograph
red dots = microaneurysms
yellow-white hard exudates blots = protein and lipid deposition in renal veins
treatment for diabetic retinopathy
laser treatment aims at stabilising changes
does not improve sight
if given at the correct stage it is very effective
what feature can you see in advanced diabetic retinopathy
cotton wool spots are seen in maculopathy
caused by the fibrosis
what are the microvascular complications of diabetes
retinopathy
neuropathy
nephropathy
what are the macrovascular complications of diabetes
stroke
cardiovascular disease (leading cause of mortality)
peripheral vascular disease
pathogenesis of diabetic nephropathy
- hyperglycaemia leads to formation of advanced glycosylation endproducts
- these accumulate in the basement membrane and cross link with collagen
- thickening of basement membrane
- membrane becomes more permeable
- glomerular hyperperfusion and hyperfiltration occurs
- increases likelihood that proteins will pass through
what is the hallmark of the clinical presentation of diabetic nephropathy
proteinuria - urine dipstick test
difference between when clinical presentation of diabetic nephropathy in type 1 and type 2 patients
type 1 : develops 5-10 years after diagnosis
type 2 : may already be present at the time of diagnosis
ways to slow progression of diabetic nephropathy
about controlling proteinuria by: good glycaemic control blood pressure control blockage of RAAS with ACE-inhibitors cholesterol control
need to intervene and treat aggressively to stop declining renal function
example of an ACE-inhibitor
Ramipril
Example of a statin
simvastatin
why is diabetes a huge risk factor for cardiovascular disease
most diabetic patients are dyslipidemic
dyslipidemia is highly correlated with atherosclerosis
atherosclerosis is associated with nearly all CVD
what is peripheral vascular disease
decreased perfusion due to macrovascular disease at more distal sites
symptoms of peripheral vascular disease
intermittent claudication
rest pain
signs of peripheral vascular disease
pulselessness, pain, pallor, paresthesia and paralysis
5 Ps
how to evaluate peripheral vascular disease
Doppler pressure studies measures the amount of blood flow through arteries and veins
treatment of PVD
stop smoking
walk through the pain
surgical intervention may be needed
what is diabetic neuropathy
a decrease in sensation in the glove and stocking distribution
pathogenesis of the pain is unknown
treatment for DN
no cure, so most treatment is symptomatic to reduce their pain
- good glycaemic control
- paracetamol
- anticonvulsants e.g gabapentin
- opioids e.g tramadol
- IV lignocaine
- amitriptyline
what is the progression of treatment for diabetic neuropathy
work up the analgesics ladder
paracetamol –> gabapentin –> tramadol
Risk factors for developing diabetic neuropathy
hypertension smoking high HbA1c duration of diabetes high BMI increase in triglycerides
consequences of diabetic neuropathy
diabetic foot ulceration which can lead to amputation
what is the progression from diabetic neuropathy to amputation
- neuropathy
- trauma
- ulcer
- failure to heal
- infection
- amputation
symptoms of diabetic neuropathy
pain (burning, paraesthesia, allodynia, worse at night)
autonomic (orthostatic hypotension, constipation, ED)
insensitivity (foot ulceration, infection)
pathophysiology of diabetic foot
- trauma happens to the foot (patient cannot feel this as have lost sensitivity so have no feeling of pain)
- this can lead to ulcer formation
additionally :
- because of deformities in the foot there is more pressure on metatarsal heads so calluses build up which can push against healthy skin underneath and damage it
- can get autonomic nerve damage i.e no sweating so get cracks and fissures and allow infection to sit it
investigation of diabetic foot
early recognition is vital!!!!
- test sensation
- 10mg monofilament
- neurotips - vibration perception
- tuning fork - ankle reflexes (may be absent)
- look at shoes for any foreign bodies
- look at the feet - any skin changes e.g pallor, decreased temp
- look for the presence of any ulcers
- pulses - doralis pedis, posterior tibial
management of diabetic foot
educate patient
daily foot inspection
comfortable and therapeutic shoes
regular chiropody to remove callus as haemorrhage and tissue necrosis may occur leading to ulceration
what is the management if the patient has a foot ulcer
MDT clinic every 2 weeks until the ulcer has healed pressure relieving footwear podiatry revascularisation antibiotics in infected
treatment if the infected diabetic foot ulcer does not heal
amputation
what increases the likelihood of infection in diabetic foot ulcers
poorly controlled diabetes impairs the function of polymorphonuclear leukocytes leading to an increased susceptibility of infections
what are the different hormone classes
peptide
amine
cholesterol derivatives and steroids
how are peptide hormones transported
water soluble, unbound
how to peptide hormones bind
cell-surface receptor
action of steroid hormones
- diffuse through plasma membrane (because they are lipid soluble)
- steroid hormone binds to receptors
- receptor-hormone complex enters the nucleus
- receptor hormone complex binds to glucocorticoid response elements
- binding initiates transcription of gene to mRNA
- mRNA directs protein synthesis
3 hormone receptor locations
cell membrane
cytoplasm
nuclear receptor family
what are the three releasing factors (stimuli) that control hormone secretion
humoral stimulus : hormone release caused by altered levels of certain ions or nutrients
neural stimulus : hormone release caused by neural input
hormonal stimulus : hormone release caused by another hormone release (e.g tropic hormone)
location of the pituitary gland
bottom of the brain
sits on top of the sella turcica of the sphenoid bone
hypothalamus sits on top of the pituitary
what connects the hypothalamus to the pituitary gland
pituitary stalk / infundibulum
what are the 6 hormones secreted by the anterior pituitary gland
- adrenocorticotropic hormone (ACTH)
- Thyroid stimulating hormone
- Growth hormone
- Luteinizing hormone
- Follice stimulating hormone
- Prolactin
what are the two hormones stored in the posterior pituitary gland
- Vasopressin
2. Oxytocin
what are the three distinct layers of the adrenal gland and what hormone do they secrete
- zona glomerulosa : mineralcorticoids (aldosterone)
- zona fasciculata : glucocorticoids (cortisol)
- zona reticularis : androgens
what are the classes of BMI
< 18.5 : underweight 18.5-24.9 : normal 25.0 - 29.9 : overweight 30.0 - 39.9 : obese > 40 : morbidly obese
what is the process of food intake
- take in food
- energy balance increases
- fat stores increase
- insulin and leptin are released
- these act on the CNS (catabolic effect to increase metabolic activity, increase physical activity and decrease food uptake)
- if we lose energy the opposite happens
- leptin and insulin act on the CNS (anabolic which decreases energy expenditure and increase food uptake)
what is satiety
feeling of fullness, the disappearance of appetite after a meal
satiety cascade
- at the time we should be eating we start to have expectations. smell food and see food. increases satiety
- start eating because you are hungry and start to become satiated and appetite goes away
- food goes down into the mouth and down stomach. stretch receptors and glucose in stomach. there is feedback on the brain to tell brain that you are getting full
- stop eating
where is the satiety centre of the brain located
ventromedial hypothalamic nucleus
hormone that is secreted in the hypothalamus that increases appetite
neuropeptide Y
three main hormones that regulate appetite
leptin (expressed in white fat) peptide YY (SI, pancreas, colon) cholecystokinin (duodenum)
action of leptin
binds to leptin receptor and switches off appetite
action of peptide YY
inhibits gastric motility and reduces appetite by binding to NPY receptors
action of cholecystokinin
binds to receptors in the pyloric sphincter to delay gastric emptying, causes gall bladder contraction and insulin release
what are the two acute metabolic emergencies caused by untreated diabetes mellitus
diabetic ketoacidosis
hyperosmolar coma
when does ketogenesis occur
In the place of carbohydate shortages when there are high rates of fatty acid oxidation and large amounts of acetyl CoA are generated that exceeds the capacity of the Kreb’s cycle is when ketone formation occurs
pathology of diabetic ketoacidosis
occurs in untreated insulin dependent diabetes
- reduced supply of glucose to cells caused by a significant decline in circulating insulin (pushes body into starvation like state)
- means there is uncontrollable lipolysis and then an increase in production of free fatty acids
- increase in fatty acid oxidation
- increased production of acetyl-CoA leads to ketone body production that exceeds the ability of peripheral tissue to oxidize them
- ketone bodies are a relatively strong acid and their increase in concentration lowers the pH of the blood
main consequence of the acidification of the blood caused by increased concentration of ketone bodies
impairs the ability of haemoglobin to bind to oxygen
risk factors for developing ketoacidosis
untreated diabetes stopping insulin therapy infection surgery pancreatitis
Clinical presentation of diabetic ketoacidosis
gradual drowsiness vomiting dehydration ketotic breath Kussmaul's breathing (deep, rapid breathing as a compensatory mechanism)
Tests for diabetic ketoacidosis
ECG, Chest X-ray
Urine : dipstick and microscopy culture and sensitivity
Blood : capillary and lab glucose, ketones, pH, U&Es, HCO3-, FBC
diagnosis of diabetic ketoacidosis
- Acidaemia (venous blood pH < 7.3)
- Hyperglycaemia (blood glucose > 11.0mmol/L) or have known DM
- Ketonaemia (>3.0mmol/L)
Treatment of diabetic ketoacidosis
- Immediate ABCs assessment
- Replace fluid loss with 0.9% saline IL over 1 hour
- Replace deficient insulin
- Give insulin with glucose to prevent hypoglycaemia
- Restore electrolyte loss and assess the need for potassium
Complications of management of ketoacidosis
cerebral oedema
hypokalaemia
coma
why do you get cerebral oedema in diabetic ketoacidosis
The osmolar gradient caused by the high blood glucose results in water shift from the intracelluar fluid (ICF) to the extracellular fluid (ECF) space
prevention of diabetic ketoacidosis
talk to the patient and evaluate compliance and educate about triggers
what is hyperosmolar hyperglycaemic state
hyperglycaemia causes an osmotic diuresis (increased urine) with hyperosmolarity leading to an osmotic shift of water into the intravascular compartment resulting in severe intracellular dehydration
is the ketogenesis in hyperosmolar hyperglycaemic state
No
insulin levels are reduced but still sufficient to inhibit hepatic ketogenesis
So no acidosis is either pH > 7.3