The adrenal gland Flashcards
Briefly describe the location and appearance of the adrenal glands
located on superior pole of the kidneys
retroperitoneal space
about 4g in adults
How does the venous drainage differ between the 2 adrenal glands (adrenal veins) and what are the implications of this?
left –> left renal vein
right –> IVC
surgery
describe the adrenal medulla
25% of adrenal gland
sympathetic ganglion derived from neural crest cells
secretes catecholamines
What does the adrenal medulla secrete? - specifics
catecholamines
norepinephrine
epinephrine - adrenaline
dopamine
Describe the adrenal cortex
75% adrenal gland
true endocrine tissue
secretes 3 classes of steroid hormones
What does the adrenal cortex secrete? - specifics
mineralocorticoids eg aldosterone
glucocorticoids eg cortisol
sex hormones eg testosterone
Why are aldosterone and cortisol essential for life?
response to stress
describe what each of the 3 zones of the adrenal cortex secrete
zona glomerulosa = aldosterone
zona fasciculata = glucocorticoids
zona reticularis = sex hormones
Is the cortex or medulla on the outside?
cortex surrounds the medulla
What are all steroid hormones derived from?
cholesterol
What determines which of the adrenal cortex hormones are produced?
the different enzymes found in the different zones
What is DHEA?
prehormone of testosterone and oestrogen which declines with age
What is 21-hydroxylase needed for?
enzyme needed for aldosterone and cortisol synthesis
What are 21-hydroxylase defects a common cause of?
congenital adrenal hyperplasia
What does 21-hydroxylase deficiency lead to?
deficiency in cortisol and aldosterone
disturbed salt and glucose balance
What happens to androgens in 21-hydroxylase deficiency?
unaffected - accumulating steroid precursors channelled into excessive androgen production
Why does 21-hydroxylase deficiency lead to adrenal hyperplasia?
decreased cortisol synthesis which removes negative feedback
ACTH increases and enlarges glands
Negative feedback from ACTH to CRH remains
Function of glucocorticoids
influence glucose metabolism
What is 95% cortisol bound to?
CBG
What kind of nucleated cells have cytoplasmic glucocorticoid receptors?
all of them
What receptors can free cortisol bind to?
cell surface
cytoplasmic
nuclear - effect transcription etc
How would you describe the pattern of release of cortisol?
circadian rhythm - preceded by ACTH similar pattern
peak 6-9 am and lowest at midnight
Why does a cortisol burst last longer than ACTH burst?
longer half life
Nadir?
lowest
What are other fluctuations of cortisol due to?
effects of other stimuli eg stress
3 reasons why cortisol is essential for life
dealing with stress by maintain [BG]
protect brain from hypoglycaemia
permissive effect on glucagon
If adrenal glands are removed what can’t the body do due to no aldosterone? how long will it take to die?
ECF maintenance
few weeks
4 glucocorticoid actions of cortisol
increased gluconeogenesis
proteolysis
lipolysis
decrease insulin resistance of fat and muscle
Is cortisol diabetogenic? why?
yes
counter regulatory effects of glucose
oppose insulin
4 non glucocorticoid effects of cortisol
negative effects on calcium balance
mood and cognition
permissive effects on norepinephrine
suppress immune system
What are the 3 things cortisol does to calcium balance and what can this lead to?
reduce absorption from gut
increase excretion at kidneys
increase bone resorption –> osteoporosis
Is hyper or hypo cortisolaemia linked to altered mood and cognition?
hyper
Action of cortisol permissive to norepinephrine
alpha receptors on smooth muscle –> vasoconstriction
vascular smooth muscle
Are high or low levels of cortisol linked to
a - hypertension
b - hypotension
a - high
b - low
What 3 things does cortisol do to the immune system?
reduce circulating lymphocytes
decrease antibody formation
inhibit inflammatory response
How can cortisol effects on immune system be used therapeutically?
asthma, ulcerative colitis, after transplantation
3 side effects of glucocorticoid therapy
muscle wastage
increase severity and frequency of infection
loss of percutaneous fat - thin, fragile skin
Action of aldosterone
act on distal tubule of kidney to determine levels of minerals absorbed and excreted
Aldosterone effects on sodium and potassium
increase sodium reabsorption
promote potassium excretion
How is aldosterone secretion primarily controlled?
RAAS originating in kidneys
Explain how increased aldosterone effect on bp
increased sodium and water retention
loss of potassium
increase blood volume
increased bp
Most common causes of cushings
tumour in adrenal cortex or pituitary
Adrenal cortex tumour - cushings syndrome or disease?
syndrome
Pituitary tumour - cushings syndrome or disease?
disease
most common - excess ACTH
Other cause of cushings
iatrogenic
Addison’s disease
hyposecretion of all adrenal cortex hormones
autoimmine attack on adrenal cortex
Describe the appearance of a patient with cushings disease
loss of fat - catabolic - wasting of extremities
redistribution of fat to face and trunk
moon face
Due to CRH and ACTH being released by stress what as an interesting link which is becoming of interest?
mental state and immune system
Do alcohol, caffeine and lack of sleep activate or inhibit HPA?
inhibit
Alcohol effect on cortisol
depress neurons involved in negative feedback
increase ACTH and CRH
How is stress linked to immune system?
cortisol elevation due to alcohol eg depressing negative feedback
cortisol has immune depressing effects
Do adrenal medulla post ganglionic fibres have axons?
no
What is a pheochromocytoma?
rare neuroendocrine tumour of adrenal medulla
Why does pheochromocytoma lead to increased bp?
increased catecholamines released
increase HR, CO and bp
Are pheochromocytoma’s diabetogenic? why?
adrenergic effect on glucose metabolism
Treatment for pheochromocytoma
responds well to surgery
sites of endocrine pathologies eg primary and levels of CRH, ACTH and cortisol
primary - low, low, high
secondary - low, high, high
tertiary - high, high, high
Why must care be taken when stopping long term steroids?
exogenous steroids enhance negative feedback
Decrease ACTH and CRH
loss of trophic action of ACTH on adrenal gland
What happens to size of adrenal gland on long term steroids and the importance of this
atrophy
risk of adrenal insufficiency if withdrawl too fast
