Adrenal gland Flashcards
what are the 3 zones of the adrenal cortex?
glomerulosa
fasciculata
reticularis
what hormone(s) does the medulla of the adrenal gland secrete?
catecholamines i.e. norepinephrine, epinpehrine (mainly) , dopamine
what hormone (s) does the cortex of the adrenal gland secrete?
glomerulosa - minerocorticoids i.e. aldosterone
fasciculata - glucocorticoids i.e. cortisol
reticularis - asex steroids i.e. testosterone, orstrogen
what is the function of the minerocorticoids?
regulation of Na and K
when plasma vol is decreased, it increases Na retension and K loss
if the plasma vol is increased vice versa
what is the medulla of the adrenal gland derived from?
neural crest tissue
its a modified sympathetic ganglion
a deficiency in what enzyme causes congenital adrenal hyperplasia?
21 hydroxylase
how does a deficiency in 21 hydroxylase cause adrenal gland hyperplasia?
a deficiency in 21 hydroxylase results in a deficiency of cortisol and aldosterone
with a decrease in those hormones there is no negative feedback on the CRH and ACTH to stop releasing hormones which act on the adrenal gland
increased ACTH is responsible for enlargement of adrenal glands
what is the difference is the busts of release of ACTH and cortisol and why?
bursts of cortisol persists longer than ACTH because it is a steroid hormone therefore has a longer half life whereas ACTH is a peptide hormone which has a short half life
what hormone released from the adrenal glands is repsonsible for glucose metabolism?
cortisol
how does cortisol affect glucose metabolism?
enhances gluconeogenesis and glucose production
proteolysis - breaks down protein to provide gluconeogenic substances to the liver
lipolysis - for alternative food supply for BG (FFA) and another substrate for gluconeogenesis (glycerol)
decreases insulin sensitivity of muscle and adipose tissue (insulin dependant tissues)
what effect does cortisol have on Ca balance?
net effect decreases Ca plasma levels
it increases Ca excretion from kidneys and decreases absorption from the gut
also increases Ca resorption of bone but net effect is a decrease
how does excess cortisol cause hypertension?
cortisol has permissive effects of norepinephrine on vascular smooth muscle = vasoconstriction
= hypertension
what effect does cortisol have on the immune system?
cortisol suppressess the immune system by reducing lymphocyte count
also reduces antibody formation and inhibits inflammatory responses
how can glucocorticoids be used to treat inflammatory conditions?
cortisol has anti inflammatory properties as it acts on the nucleus switching off the expression of inflammatory markers
what are the side effects of glucocorticoid therapy?
increased severity / frequency of infection (suppress immune system)
loss of percutaneous fat stores = thinning of skin = fragile (because it cause increase in lipolysis)
muscle wasting (causes protein catabolism)
osteoporosis (increases bone resorption of Ca)
what is the secretion of minerocorticoid controlled by?
renin angiotensin aldosterone production
does an increase in aldosterone cause an increase or decrease in BP?
aldosterone causes Na retension and K depletion therefore causing an increase in blood vol and BP
name a conditon caused by hyperexcretion of cortisol and hyposecretion of cortisol.
hyper = cushings hypo = addisons
what can be the cause of cushings?
a tumour in the adrenal cortex (primary)
a tumour in the pituitary gland (secondary)
what is the most common cause of cushings?
pituitary tumour causing an excess of ACTH production and therefore cortisol
what is the presentation of someone with cushings?
wasting of the limb muscles
distribution of fat in the trunk and face (giving moon face appearance)
hump at the top of the back as fat collects there
what effect does alcohol have on the production of CRH and ACTH?
alcohol depresses the neurones involved in the negative feedback on ACTH and CRH release
therefore causes increased production levels
how doess stress, alcohol and lack of sleep result in a depressed immune system?
stress & lack of sleep promotes the release of CRH and ACTH.
alcohol inhibits the negative feedback on ACTH and CRH
therefore this further enhances the release of CRH, ACTH and therefore cortisol
cortisol diminishes the immune system by reducing lymphocytes and inhibiting antibody formation
what is characteristic about the presentation of phaeochromocytomas?
presents with ‘episodes’ of symptoms
