Obesity Flashcards
Why is studying obesity important?
Predisposes development of type II diabetes
Define obesity
Excess accumulation of fat in the body
What are the 4 ways obesity can be measured?
> BMI
Waist to hip ratio
Skin fold calliper test
Calculate proportions of muscle to fat to water
What is BMI?
What do the different ranges indicate?
Body mass index
= mass/height^2
20-25 = normal 25-30 = grade I 30-40 = grade II 40+ = morbidly obese = increase risk of death
What are the 3 causes of obesity?
> Increased food consumption + reduced energy expenditure
Genetic causes
Pathological = disease causing process that results in obesity
What is leptin?
Protein w/ 167 amino acids
- acts like a hormone (reduces Neuropeptide Y production)
- produced by adipocytes
- controls appetite
What is the name of the gene that encodes leptin?
OB gene
How can the OB gene cause obesity?
What is this condition known as?
Homozygous mutation in OB gene
- -> leptin not produced/ non-functional
- -> appetite never sated
Ob/Ob
Describe how appetite is controlled
- Adipocytes secrete leptin into blood stream
- Leptin reaches hypothalamus + binds to leptin receptor
- -> reduced production of Neuropeptide Y
- -> increased energy expenditure + reduced food intake
How does Ob/Ob lead to a patient always being hungry?
- Don’t produce leptin
- Neuropeptide Y produced all the time
- Decreased energy expenditure + increased food intake
- Always hungry
Give an example of a pathological cause of obesity
Cushing’s disease
Describe a cushingoid appearance
> moon face > truncal obesity > striae (stretch marks) > thin extremities/ limbs due to muscle wasting > diabetic > buffalo hump
What can Cushing’s be due to?
Adenoma in pituitary gland
Adrenal tumour
What is an adenoma?
Benign tumour of epithelial origin
What are the 2 types of adenomas?
Microadenoma
= less than 10mm
Macroadenoma
= more than 10mm
What are the 2 regions of the pituitary gland?
Anterior
Posterior
What does the anterior region of the pituitary gland secrete and by which cells?
Basophilic cells: > FSH > LH > ACTH > TSH
Acidophilic cells:
> GH
> prolactin
What does FSH stand for?
Follicle stimulating hormone
What does LH stand for?
Luteinising hormone
What does ACTH stand for?
Adrenocorticotropic hormone
What does TSH stand for?
Thyroid stimulating hormone
What does GH stand for?
Growth hormone
What does the posterior region of the pituitary gland secrete?
Oxytocin
Vasopressin
What are the regions of the adrenal gland?
Cortex
Medulla
What does the medulla of the adrenal gland do?
Produces catecholamines: epinephrine + norepinephrine
What does the cortex of the adrenal gland do?
Corticosteroids:
> cortisol
> mineralocorticoids
> sex steroids
What are the 3 layers of the cortex from outside to the medulla?
Zona Glomerulosa
Zona Fasciculata
Zona Reticularis
What is the normal function of cortisol?
Raises blood glucose levels
What happens in normal circumstances when the pituitary gland secretes ACTH?
What is this an example of?
- Causes cortex of adrenal gland to secrete cortisol
- Prevents ACTH secretion
Negative feedback
How can a pituitary adenoma lead to Cushing’s?
- Increase in ACTH
- Increase in cortisol
- Cells in tumour don’t respond to cortisol
-> cortisol levels remain high
=hypercortisolaemia
How can adrenal tumours lead to Cushing’s?
Increase cortisol levels
=hypercortisolaemia
What are the 4 clinical presentations of Cushing’s disease?
> cushingoid appearance
headache
bitemporal hemianopia
hypercortisolaemia
What are headaches in Cushing’s caused by?
Stretching of dura matter
-> Swelling of the meninges
What are the meninges?
3 layers of protective tissue: > dura > arachnoid > pia ...that surround the brain + spinal cord
What is bitemporal hemianopia?
Loss of 1/2 field of vision
How are optic nerves orientated?
Where does the pituitary gland sit?
Optic nerves cross over
-> optic chiasma = point of cross
Sits at optic chiasma
How do pituitary adenomas cause bitemporal hemianopia?
Pituitary gland sits below optic chiasma
->swelling of adenoma presses on it
What are the 3 effects of Hypercortisolaemia?
> increases gluconeogeneis
redistribution of body fat
muscle wasting
Describe the Cori cycle
- lactate in contracting muscles carried to liver
- converted into glucose
- glucose can go back to liver (as glycogen) or back to muscle
How does Hypercortisolaemia increase gluconeogenesis?
Cortisol stimulates production of more enzymes for gluconeogenesis
How does Hypercortisolaemia cause redistribution of body fat?
Cortisol may cause lipid breakdown
How does Hypercortisolaemia cause muscle wasting?
Cortisol inhibits protein synthesis + increases protein degradation
Define iatrogenic
Unwanted side-effects due to drugs
Why might somebody take cortisol?
> adrenal glands removed
reduced ATCH/cotrisol
anti-inflammatory
What are the side effects of taking cortisol?
Can produce cushingoid characteristics
- as produce own cortisol endogenously + taking extra cortisol
What are the most likely deaths due to obesity?
> coronary heart disease > diabetes > arthritis > gall stones > varicose veins + haemorrhoids > increased risk of death during surgery > decreased lung capacity
Why are obese people more likely to die during surgery?
Surgery takes longer due to being bigger
Difficult to maintain anaesthetic as it dissolves into fat over time
How can obesity lead to AAGA in surgery?
- Anaesthetic dissolves into fat over time
- anaesthetic levels in blood decreases
- patient wakes up
What is AAGA?
Accidental awareness of general anaesthesia
How can obesity lead to decreased lung capacity?
Fat presses on lungs
- > reduces lung capacity
- > reduces lung function
What can a reduced lung capacity predispose?
Bronchitis
Pneumonia
What are the 2 things that can result from coronary heart disease?
Heart attack
Stroke
What are the 2 types of cells that respond to insulin + take up glucose?
Adipocytes
Muscle cells
- cardiac
- skeletal
Describe what happens to a fat/muscle cell when glucose levels are low
Insulin levels are also low
->GLUT4 remain within the cell
Describe what happens to a fat/muscle cell when glucose levels are high
High insulin levels -> binds to insulin receptor -> GLUT4 moves to membrane (translocation) -> glucose enters cell
What happens in obese people in terms of insulin?
Insulin resistance
= cells unable to sense insulin
= type II diabetes
How can Cushing’s lead to diabetes?
Increased cortisol
-> inhibits affect of insulin on GLUT4 movement to membrane
-> blood glucose levels increase
= diabetes
What is the function of insulin?
Lowers blood glucose conc
- stimulates body to store glucose for when needed
Why are obese people at a higher risk of developing diabetes?
Have increased levels of fatty acids
-> decrease in glucose uptake into muscle + decrease in glucose utilisation
-> increase in blood glucose
= diabetes
Why do obese people get arthritis?
Increased pressure on weight-bearing joints e.g. knees + hips
(exacerbates issue as can’t exercise)
How do gall stones form?
When bile salts + cholesterol precipitate
What are varicose veins?
Tortuous blood vessels on legs
How do varicose veins form?
Increased pressure on veins
-> leaky valves
-> blood pools
= tortuous blood vessels on surface of leg
What are haemorrhoids?
Enlargement of spongy blood vessels around anus
What are the causes of haemorrhoids?
Increase in intra-abdominal pressure
Decrease in fibre intake
-> increased straining on defecation
What are the 3 degrees of haemorrhoids?
1st - bleed at end of defecation
2nd - protrude + return
3rd - remain outside
What are the treatments for haemorrhoids?
Non-surgical:
- inject irritant fluid
- -> shrivel up
Surgical:
- elastic band OR cut off
What is muscle wasting in Cushing’s due to?
Increased cortisol levels on protein metabolism
How does cortisol affect protein metabolism?
Reduces protein synthesis
Increases protein breakdown
