endocrinology Flashcards
health implications of obesity
heart disease stroke depression sleep apnoea type 2 diabetes osteoarthritis cancer liver disease reproductive complication
poor nutrition in childhood
emotional and behavioural= stigma, bullying, self esteem
education= school absence
physical health
obesity
BMI >30
>40= morbidly obese
obesity prevalence
around 60% of UK is overweight or obese
prevalence is increasing
inequalities of obesity
ethnicity
education
national action for obesity
labelling sugar eduction schools retail marketing
endocrinology
study of hormones and their gland of origin, their receptors, intracellular signalling pathways and associated diseases
hormone
to excite
endocrine
within
glands pour secretions into blood stream
exocrine
outside
glands pour secretions through a duct to side of action
hormone action
endocrine- act at distant sites
paracrine- act on adjacent cells
autocrine- feedback on same cell that secreted hormone
fat soluble hormones
transport= protein bound
cell interaction=diffuse into cell
half-life=long
clearance=slow
water soluble hormones
transport=unbound
cell interaction=surface receptor
half-life=short
clearance=fast
hormone classes
peptide
amines
iodothyronines
cholesterol derivatives and steroids
peptides
- vary in length
- linear or ring structure
- stored in secretory granules
- water soluble
- released in pulses or bursts
peptide hormone storage
synthesis= preprohormones -> prohormone
packaging= prohormones -> hormones
storage and secretion= hormones
insulin receptors
insulin binds and phosphorylation of receptor occurs
tyrosine kinase now active
signal molecules are phosphorylated causing cascade effect and glucose is taken in
amines
derive from tyrosine
adrenoceptor activation
stimulate sympathetic nervous system
alpha and beta adrenoceptors
iodothyronines
- 99% are protein bound as fat soluble
- 20% of T3 is secreted from thyroid: thyroglobulin released into colloid acts as a base for TH synthesis
- iodine and tyrosine molecules form -iodothyronines
- conjugation of these gives rise to T3 and T4 and stored in colloid, bound to thyroglobulin
synthesis of thyroxines
- Thyroglobulin is synthesised and discharged into the follicle lumen
- Iodide is actively transported in
- Iodide is oxidised to iodine
- Iodine is attached to tyrosine in colloid, forming
DIT and MIT - Iodinated tyrosines are linked together to form
T3 and T4 - Thyroglobulin colloid is endocytosed and combined with a lysosome
- Lysosomal enzymes cleave T4 and T3 from thyroglobulin and hormones diffuse into
bloodstream
hormone receptors in cell membrane
peptide
hormone receptors in cytoplasm
steroid
hormone receptors in nucleus
thyroid hormone
oestrogen
vitamin D
steroid action
diffuses through plasma membrane and binds to receptor
receptor-hormone complex enters nucleus and binds to GRE
this initiates transcription of gene into mRNA
this directs protein synthesis
control of hormone secretion
basal secretion= continuously pulsatile
superadded rhythms e.g. day/night cycle
release inhibiting factors
releasing factors
diurnal rhythms
biological rhythm that is synchronised with day/night cycle
may or may not be a circadian rhythms
hormone metabolism
increased metabolism to reduce function
hormone receptor induction
e.g. induction of LH receptors by FSH in follicle
hormone receptor down regulation
hormone secreted in large quantities cause down regulation of its target receptors
synergism
combined effects of two hormones amplified
antagonism
one hormone opposes the other hormone
negative feedback
diminution or counteraction of an effect by its own influence on the process
initial stimulus -> response -> decrease stimulus -> response loop shuts off
positive feedback
enhancing or amplification of an effect by its own influence on the process
initial stimulus -> response -> increase stimulus -> outside factor required to shut off
vasopressin release
increased osmolarity
decreased blood volume
nausea, vomiting, stress, exercise
vasopressin action
increased ACTH
vasonconstriction
increased H2O retention
oxytocin release
suckling
uterine contractions
oxytocin action
milk ejection
labour
pituitary dysfunction
tumour mass effects
hormone excess
hormone deficiency
investigate with hormonal test and MRI
thyroid hormones function
- accelerates food metabolism
- increases protein synthesis
- stimulation of carb metabolism
- enhances fat metabolism
- increase CO of and HR
- growth rate accelerated
- brain development during foetal life
T4 and T3 half life
T4 turns into T3
half life of T4 is 5-7 days
t3 is 1 day
cortisol action
metabolic and stress hormone
stimulates gluconeogenesis
activates anti-stress and anti-inflammatory pathway
adrenals
steroids: -mineralocorticoids -glucocorticoids -androgens amino-acid derived (produced in adrenal medulla): -epinephrine -norepinephrine
androgens
androstenedione
dehydroepiandrosterone (DHEA)
produced in zona reticularis
glucocorticoids
cortisol androgens
produced in zona fasiculata
mineralocorticoids
aldosterone
produced in zona glomerulosa
adrenal hormones in short term stress
HR and BP increased
bronchioles dilate
glycogenolysis
reduced blood flow to digestive system and urine output
adrenal hormones in long-term stress
kidneys retain sodium and water
blood volume and BP rise
proteins and fats converted to glucose -> blood glucose increases
immune system suppression
endocrine tissues
pituitary thyroid parathyroid adrenal pancreas ovary testes
other hormone tissues
heart- atrial natriuretic peptide liver- insulin like growth factor (IGF-1) kidney- erythropoietin Gi tract- gastrin lung blood vessels
appetite
desire to eat food
hunger
need of eating
anorexia
lack of appetite
satiety
feeling of fullness
BMI definition
weight (kg)/ height (m2)
BMI categories
<18.5 underweight 18.5-24.9 normal 25-29.9 overweight 30-39.9 obese >40 morbidly obese
health risk of obesity
type 2 diabetes hypertension coronary artery disease stroke osteoarthritis cancer obstructive sleep apnoea
obesity and sleep
shift work is associated with increased obesity
metabolic circadian rhythm- cortisol levels are higher and leptin levels are lower- increasing risk of obesity with sleep deprivation
why we eat
internal physiological drive
external psychological drive
feelings that prompt thought of food
nutrients
highly refined sugar= quick and short satiety
low glycaemic index food= slower and longer satiety
high protein= prolonged satiety
hypothalamus and appetite
lateral hypothalamus = hunger centre
ventromedial hypothalamic nucleus= satiety centre
leptin
expressed in white fat
binds to leptin receptor
switches off appetite and is immunostimulatory
blood levels increase/decrease after meal/fasting (respectively)
peptide YY
secreted by neuroendocrine cells in ileum, pancreas and colon in response to food
inhibits gastric motility and reduces appetite
cholecytstokinin
receptors in pyloric sphincter
delays gastric emptying
gall bladder contraction
insulin release
ghrelin
stimulates appetite
blood levels high when fasting
