HPA axis Flashcards
What does HPA do?
Stress response
Pituitary - kidneys - adrenal gland
What happens when you’re stressed?
Hypothalamus releases CRH
Pituitary releases ACTH
ACTH stimulates release of cortisol from cortex
Mobilises energy from glucose
What is the Adenohypophysis?
Anterior pituitary
What is the neurohypophysis?
Posterior pituitary
What is produced by posterior pituitary?
ADH and oxytocin
What does the portal vein do?
Takes hormones to pituitary
Where is cortisol released?
Adrenaline;s
Where is CRH released?
Hypothalamus
What does cortisol do in stress?
Increases gluconeogenesis - increases BP and glucose for fight/flight
Inhibits CRH and ACTH release
What does zona glomerulosa do?
Aldosterone production, increased sodium reabsorption, increased potassium excretion
What does zona fasciculata do?
Cortisol production, increased gluconeogenesis, increased BP
What does zona reticular do?
Androgens to be converted to sex hormones
What does medulla do?
Adrenaline/noradrenaline
Fight or flight
What does cortisol do?
Steroid
Gluconeogenesis
Immunosuppression
Anti-inflammatory effects
What is Addison’s disease?
Primary adrenal failure - complete lack of cortisol and mineralocorticoids
Main cause is TB
What is an Addisonian crisis?
Medical emergency, body shutdown, low BP and salt, hypoglycaemic
How are pituitary and adrenal failure linked?
If pituitary can’t make ACTH then adrenals won’t make cortisol
Sodium, potassium, cortisol and ACTH in Addison’s
Low sodium, high potassium, low cortisol, high ACTH
Why does Addison’s lead to hyperpigmentation?
Metabolite from converting POMC to ACTh is melanocyte stimulating hormone
How to investigate Addison’s further
Give synthetic ACTH - in primary failure it will have no impact on cortisol b
How to treat Addison’s
Hydrocortisone IV
What causes Cushing’s disease?
Excess cortisol
Overstimulation of adrenals by ACTH or overproduction of cortisol from adrenals
What does iatrogenic mean?
We have caused the problem
How are Cushing’s disease and Cushing’s syndrome connected?
Cushing’s disease - pituitary tumour - increased cortisol
Symptoms of Cushing’s disease
Hypertension, hyperglycaemia, moon face, buffalo hump, easy bruising, obesity, hypokalaemia
Why does Cushing’s lead to weight gain?
Cortisol = more gluconeogenesis = hyperglycaemia = weight gain
Main cause of Cushing’s
Pituitary tumour producing ACTH
Differences between primary and secondary cause
Primary is ACTH independent
Secondary is ACTH dependent
How to test for primary or secondary cause
Dexamethasone has no impact on primary
CRH test
Cortisol levels rise in secondary
