The adrenal gland Flashcards by Birwe Leon

Briefly describe the location and appearance of the adrenal glands

located on superior pole of the kidneys
retroperitoneal space
about 4g in adults

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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

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describe the adrenal medulla

25% of adrenal gland
sympathetic ganglion derived from neural crest cells
secretes catecholamines

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What does the adrenal medulla secrete? - specifics

catecholamines
norepinephrine
epinephrine - adrenaline
dopamine

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Describe the adrenal cortex

75% adrenal gland
true endocrine tissue
secretes 3 classes of steroid hormones

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What does the adrenal cortex secrete? - specifics

mineralocorticoids eg aldosterone
glucocorticoids eg cortisol
sex hormones eg testosterone

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Why are aldosterone and cortisol essential for life?

response to stress

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describe what each of the 3 zones of the adrenal cortex secrete

zona glomerulosa = aldosterone
zona fasciculata = glucocorticoids
zona reticularis = sex hormones

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Is the cortex or medulla on the outside?

cortex surrounds the medulla

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What are all steroid hormones derived from?

cholesterol

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What determines which of the adrenal cortex hormones are produced?

the different enzymes found in the different zones

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What is DHEA?

prehormone of testosterone and oestrogen which declines with age

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What is 21-hydroxylase needed for?

enzyme needed for aldosterone and cortisol synthesis

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What are 21-hydroxylase defects a common cause of?

congenital adrenal hyperplasia

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What does 21-hydroxylase deficiency lead to?

deficiency in cortisol and aldosterone

disturbed salt and glucose balance

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What happens to androgens in 21-hydroxylase deficiency?

unaffected - accumulating steroid precursors channelled into excessive androgen production

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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

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Function of glucocorticoids

influence glucose metabolism

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What is 95% cortisol bound to?

CBG

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What kind of nucleated cells have cytoplasmic glucocorticoid receptors?

all of them

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What receptors can free cortisol bind to?

cell surface
cytoplasmic
nuclear - effect transcription etc

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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

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Why does a cortisol burst last longer than ACTH burst?

longer half life

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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?

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