Endocrine Principles Flashcards
examples of peptide hormones
oxytocin
GH
FSH
what amino acid is adrenaline derived from
tyrosine
what amino acid is melatonin derived from
tryptophan
describe the action ofd tyrosine kinase receptors and what hormone receptor is TK
extracellular region that acts with ligand, translated to tyrosine kinase domain intracellularly
Insulin
describe the action of GPCR, their transmembrane domain
7 fold transmembrane domain
ligand binds to extracellular domain to evoke intracellular response by intracellular domain activating alpha/beta/gamma subunits to mediate effect
what hormones utilise steroid hormone receptors and how do they work
intracellular in cytoplasm or nucleus and bind to DNA response elements to evoke change in gene transcription
oestrogen, testosterone, glucocorticoid
describe the hypothalamic-pituitary axis
specialised neurons in hypothalamus release specific hormones to act on pituitary gland to release endocrine glands
controlled by -ve feedback
factors affecting clinical hormone measurement
pattern of secretion carrier protein presence interfering agents hormone stability and 1/2 life absolute concn
true/false - thyroid function should be measured in acute illness
false - it forms little value unless considered central to clinical practice, ie thyroid storm
describe the thyroid axis
hypothalamus releases TRH to anterior pituitary to release TSH
TSH stimulated thyroid to release FT4, FT3, liothyronine
FT4 and FT3 have negative feedback on pituitary and hypothalamus to keep concn in a narrow window
raised TSH with low FT4 and FT3 is indicative of?
hypothyroidism
low TSH with high FT4 and FT3 is indicative of?
hyperthyroidism
when is TSH not a reliable marker of thyroid function
anterior pituitary dysfunction
describe the hypothalmic-pituitary-adrenal axis
hypothalamus secretes CRH to ant pituitary to release ACTH on adrenal cortex tp secrete cortisol
-ve feedback on ant pituitary and hypothalamus
what rhythm does cortisol production have and rescribe it
circadian
rise in morning and slowly drops over day until nearly zero at night
rises again in anticipation for day ahead
describe the hypothalamic-pituitary gonadal axis
hypothalamis neurons stimulated to cause GnRH secretion to act on ant pituitary to release FSH/LH
these can also act on endocrine cells to secrete steroid/peptide hormones
-ve feedback
rhythm of testosterone
highest in morning, dips and begins to rise again early evening and overnight
circadian
describe prolactin secretion
secreted by ant pituitary but under inhibitory control by tonic dopamine
after secretion excess prolactin -ve feedback to hypothalamus to increase dopamine secretion again
dynaic testing - a suppression test is used for
hormone excess
dynamic testing - a stimulation test is used for
hormone deficiency
what is primary adrenal failure also known as
addisons disease
what is an excess of cortisol known as and what are possible causes
cushings syndrome
exogenous steroids
pituitary/adrenal origin
ectopic ACTH
stimulation test for addisons?
synacthen test
stimulation test for cushings and how does ACTH help
dexamethasone suppression test
failure to suppress is cushings
measure of high ACTH determines whether its cushings or ectopic ACTH
measure of low ACTH implies adrenal origin
features of cushings syndrome
cushingoid appearance hirtuism acne abdominal striae interscapular fat pad proximal myopathy osteoporosis hypertension impaired glucose tolerance
autocrine regulation
chemicals released from cells bind to receptors on the cells that are releasing them
paracrine regulation
cell modulates an adjacent cell
endocrine regulation
chemicals released from secretory cells into circulatory cells to reach target tissue and evoke response
what are hormones
substance elaborated by one cell to regulate another by autocrine, paracrine or endocrine route
what does the hypothalamus do
controls activity of secretion of ant pituitary
controls post pituitary by neural control
synthesises post pituitary hormones
neural control over adrenal medulla
how do steroid hormones travel in blood
travel either free or bound to carrier proteins
mechanism of action of steroid hormones
diffuse through cell membrane
bind to hormone receptor to form a complex within the cell
binds to DNA to activate specific genes
leads to production of key substances
true/false - amine derived hormones such as catecholamines or thyroid hormones cannot be stored in their synthesising organ
false - they can
describe insulin secretion from elevated blood glucose
increased blood glucose travels into B cell by GLUT2
converted to G-6-P by glucokinase and metabolised in the metabolism
ATP acts to close ATP K channel and cause membrane depolarisation
opening of Ca channels increases intracellular Ca and so triggers secretion of insulin
what effects do carrier proteins have on hormone transport
facilitates transport
increases half life
reservoir for hormone
how can those with leptin deficiency/defective receptors develop diabetes?
leptin in high quantities can suppress appetite and increase thermogenesis so in lack of receptor or leptin this can cause unrestrained appetite
mechanism of action of orlistat
lipase inhibitor so blocks up to 1/3 ingested fat being absorbed
3 types of bariatric surgery?
gastric bypass
sleeve gastrectomy
roux-en-Y gastric bypass
why is is harder to lose weight at a lower weight
adaptive thermogenesis -resting metabolic rate is higher in obese and falls in weight loss
lower the BMR the harder it is to lose this weight and keep it off
what do alpha cells secrete
glucagon
what do beta cells secrete
insulin
waht do delta cells secrete
somatostatin
what do PP cells secrete
pancreatic polypeptide
what do epsilon cells secrete
ghrelin
true/false - in T2DM glucagon secretion is suppressed
false - due to insulin resistance glucagon may remain active and so can lead to further hyperglycaemia
what is the incretin effect
oral glucose administration induces greater insulin secretion than IV administration of an isoglycaemic dose of insulin
this is because GLP-1 is produced to stimulate beta cells further
what breaks down GLP-1
DPPIV
