Adrenal Tutorial Flashcards
from top to bottom list the layers of the adrenal glands
connective tissue cortex: zona glomerulosa zona fasciculata zonareticularis =bottom of cortex medulla
what controls the zona glomerulosa
renin-angiotensin system
what controls the zona fasciculata
ACTH
what controls the zona reticularis
ACTH
what controls the medulla
sympathetic NS control
what is produced by the zona glomerulosa
mineralocorticoid (aldosterone)
what is produced by the zona fasciculata
glucocorticoids- cortisol, cortisone, corticosterone
what is produced by the zona reticularis
sex hormones - dehydroepiandrosterone (DHEA)
what is produced by the medulla
catecholamines- adrenaline, nor-adrenaline
what is all steroid hormone derived from
cholesterol
what cells in the medulla make the catecholamines
chromaffin cells
what do the chromaffin cells make the catecholamines from
tyrosine
do catecholamines have a long or short half life
short
what stimulates the synthesis and release of aldosterone
angiotensin II
what does aldosterone do
increased NaCl retention and reabsorbtion within the kidney
due to osmosis water is also reabsorbed
blood volume and pressure in increased
causes loss of potassium in urine due to Na+ K +ATP ase
how else does angiotension II cause water reabsorption
working with ADH
describe the renin angiotensin cycle
(decreased NaCl, ECF volume, blood pressure)
increased renin + angiotensin = angiotensin 1 + ACE = angiotensin II acts on zona glomerulosa to make aldosterone
what is conns syndrome
where a tumour present in the cells of the zona glomerulosa secretes excess amounts of aldosterone
what is the biochem of conns
increased NaCl
increased H2O
decreased K+
what are the symptoms of conns
hypertension
hypokalaemia
does adrenal hyperplasia affect one or both adrenal glands usually
bilaterally
are adrenal hyperplasia and conns primary or secondary aldosteronism
primary
what are the symptoms of adrenal hyperplasia
sames as conns- hypertension and hypokalaemia
how do you diagnose primary aldosteronism
aldosterone to renin ratio
if ratio is above 750 then carry out a saline suppression test - if aldosterone doesnt drop by 50% then primary aldosteronism
describe a saline suppression test
2 litres of saline is administered to patient over the course of 4 hours, if aldosterone levels fail to decrease by 50% then will confirm primary aldosteronism
what is the best treatment for unilateral primary aldosteronism
unilateral conns
surgery best for decreasing blood pressure
what is the best treatment for bilateral primary aldosteronism
aldosterone receptor antagonist e.g. spirinolactone- reduces reabsorption of NaCl and H20
what are the side effects of spironolactone
nausea, rashes, gynaecomastia
can use eplerenone instead
how do angiotensin II and ACTH stimulate the adrenal glands to produce hormones
cause increase growth of the cells stimulating them to produce hormones
what are the functions of glucocorticoids (esp cortisol)
maintain plasma glucose levels
when stressed provide fuel from carbs, fats and proteins (increases lipolysis leading to increased plasma fatty acids. increase proteolysis causing increased plasma amino acids)
increases responsiveness of adrenoreceptors to adrenaline- prevents shock
anti inflammatory and immunosuppressive role
increased hepatic gluconeogenesis and decreased glucose uptake in all tissues expect the brain (both cause increased plasma glucose)
what are the signs of cortisol excess
muscle wasting central obesity cardiac output and blood flow increased (hypertension) plethoric 'moon' face (due to fat redistribution) conjunctival oedema cataracts easy bruising skin infections poor wound healing buffalo hump proximal myopathy, proximal muscle wasting (increased proteolysis) thin skin purpura red/ purple striae back pain (muscle weakness and central obesity) polydipsia and polyuria bone pain euphoria severe depression psychosis insomnia
what effect does ecess cortisol have on the immune system
decreased macrophage and cytokine activity
how does cortisol excess affect bone
reduced osteoblast activity and decreased calcium absorption- bone pain, kyphosis, osteoporosis
how does excess cortisol effect the skin
decreased collagen formation
describe the regulation of cortisol
(stress illness / diurnal rhythm) hypothalamus secretes corticotrophin releasing hormone- ant pituitary - ACTH - adrenals - cortisol (neg feeback on ant pituitary and hypothalamus)
what are the types of cushings
ACTH dependent or independent
what is the most common cause of cushings
ACTH dependent due to adenoma in the pituitary gland that produces ACTH
what are the types of ACTH dependent cushings
adenoma in pituitary gland that produces ACTH
Ectopic cancers that secrete ACTH - lung, thymus, pancreas
what other symptoms might a pituitary tumour produce
headaches and visual field impairment
what are the types of ACTH independent cushings
adrenal adenoma (most common)
adrenal carcinoma
nodular hyperplasia
in ACTH independent cushings is ACTH high or low
low
why is there oversection of sex hormones in cushings
as the zona reticularis is also stimulated by ACTH
what is seen in hypersecretion of DHEA
women: acne, amenorrhea, frontal balding, facial hair growth
men: lack of libido and impotence
what is the definitive test for cushings
low dose dexamethasone test
what is dexamethasone
very potent glucocorticoid
what result in a LLDT would show no cushings
<50 nmol/litre
what result in a LLDT would show cushings
> 100 nmol/litre suspicious of cushings
what can determine between pituitary, adrenal and ectopic cushings
high dose dexamethasone test
how does a HDDT distinguish in cushings
pituitary- suppressed by 50%
adrenal and ectopic -not supressed
what are the ACTH levels like in pituitary, adrenal and ectopic cushings
pituitary- <300
adrenal- <1
ectopic- >300
what does untreated cushing lead to
death due to complications from hypertension, diabetes mellitus, cardiovascular disease
what is the medical therapy for cushings
metyrapone- a 11beta- hydroxylase blocker that stops the synthesis of cortisol
ketoconazole works in same way and is synergistic with metyrapone
why do you need to reduce cortisol levels before surgery
as immune response still impaired
how are anterior pituitary tumour usually removed
trans-sphenoidal removal
what ca be done if surgery doesnt help cushings (pituitary)
radiotherapy
what is the surgical treatment for adrenal cushings
bilateral adrenalectomy
what cells make up the medulla of the adrenal glands
chromaffin cells
what controls the release of catecholamines from the medulla
sympathetic nervous system
what is the effect of adrenaline
increases rate and strength of heart, vasoconstrictor effect on peripheral vessels- increases blood pressure
vasodilation of the skeletal muscle- delivers more oxygen and glucose
adrenaline acts on B1 receptors on the …. to have the effect of…
heart
increased force and rate
adrenaline acts on alpha 1 receptors on …. to have the effect of…
blood vessels
vasoconstriction
adrenaline acts on B2 receptors on …. to have the effect of…
skeletal muscle
vasodilation
adrenaline acts on alpha 2 receptors on the …. to have the effect of…
islet beta cells
decreased insulin secretion
how does adrenaline affect metabolism and via what receptors
alpha and beta 1
increases gluconeogenesis and glycogenolysis
what are the symptoms of hypersecretion of adrenaline
classic triad: HPX, sweating, headaches
arrhythmias tachycardia/ bradycardia pallor excessive flushing postural hypertension anxiety polydipsia polyuria constipation paralytic ileus of the bowel
what is a phaeochromocytoma
rare catecholamine secreting tumour that arises from sympathetic paraganglia cells
what are paraganglia cells
collections of adrenaline secreting chromaffin cells
where are phaeochromocytoma found
medulla of adrenals or sympathic chain
what are paragangliomas
phaeochromocytomas found at the oartic bifurcation
what is the 10% tumour
10% extra adrenal 10% malignant 10% bilateral 10% in children 10% hereditary syndrome
what hereditary conditions are associated with phaeochromocytoma
MEN 2 (usually bilateral in this condition)
what tumours do you get in MEN 2
thyroid, parathyroid, neuro endocrine (phaeochromocytoma)
what can be used diagnose phaeochromocytoma
24hr urinary catecholamines and metabolites
CT/MRI
131 iodine MIBG (labelled with beta and gamma particles)
what is the treatment for phaeochromocytoma
complete alpha and beta blockade (atenolol, phenoxybenzamine) before surgery to prevent arrhythmias and CV complications
if malignant then chemo + 131 iodine MIBG
what can cause adrenal hypofunction
primary- addisons disease (automimme attack on adrenal glands)
secondary- pituitary problem, lack of ACTH
iatrogenic- steroids might cause adrenal glands to atrophy
how does an addisonian crisis present
high potassium, low sodium, dehydration, low glucose, abdo pain. weakness, vomiting
what is the treatment for an addisonian crisis
immediate
glucose
IV fluids
steroid replacement
what can help distinguish primary and secondary addisons
increased skin pigmentation- caused by ACTH being converted to melatonin, cant be a secondary (pituitary) cause
in addisons what causes the low sodium and high potassium
lack of aldosterone
in addisons what causes the low glucose
lack of glucocorticoids
what antibodies in addisons disease
anti-adrenal antibodies
what can determine whether the adrenal glands are working or not
synACTHen test- measure cortisol produced by adrenals in response to synthetic ACTH, should be more than 500 at 30 mins
what is congenital adrenal hyperplasia
where adrenal glands lack the enzymes needed for making steroids
- can present as acute salt loss crisis or ambiguous genitalia in early childhood, or in hirsutism in late childhood/adulthood
- treatment is steroids
what is the hormone replacement given for adrenal insufficiency
hydrocortisone - replaces glucocorticoids
fludrocortisone- given to replace aldosterone (no required in all cases)
what are the sick day rules for adrenal insufficiency and patient education points
if have period of illness then always double your dosage
dont suddenyl stop as this causes adrenal crisis even when well
carry identification that you are on steroids
what would postural hypotension raise concerns of
adrenal insufficiency
