Basic Functions of the Adrenal Glands Flashcards
What does the adrenal cortex and medulla secrete? Give examples
Cortex = corticosteroids
- zona glomerulosa: mineralocorticoids e.g. aldosterone
- zona fasciculata: glucocorticoids e.g. cortisol
- zona reticularis: androgens e.g. DHEA
Medulla = catecholamines
- adrenaline
- noradrenaline
What is the precursor for all corticosteroids?
What is the first step of conversion?
What enzyme is involved in this first step?
Cholesterol
Pregnenolone
StAR
In which sex is DHEA most important and why?
Women because in men the main androgen (testosterone) is synthesised in the testes
What is the affect of ACTH on adrenal size?
Give examples of when this might happen
low ACTH - glands shrink e.g. in exogenous steroid use
high ACTH - glands enlarge e.g. Cushing’s disease
What are the actions of glucocorticoids?
When is this important?
Increase glucose mobilisation
Maintenance of circulation
Immunomodulation
- All important during stress
How are glucocorticoids transported?
Most bound to Corticosteroid-Binding Globulin (CBG)
Some bound to albumin
5% free –> bioavailable
What happens to CBG levels during inflammation/sepsis, why is this important?
Levels decrease
Increases free cortisol
What regulates glucocorticoids?
What regulates this?
ACTH
CRH stimulates ACTH
What affects release of CRH from hypothalamus? x3
stress
cytokines
diurnal rhythm
What is the difference between circadian and diurnal
Circadian = once a day Diurnal = occurs during the day
What do mineralocorticoids do?
Where do they act?
Regulate salt and water balance primarily in the kidneys, some in salivary/sweat glands, dancers and colon
What are the causes of endocrine salt loss?
What are the plasma and urine levels of sodium and potassium?
Primary adrenal insufficiency
or End Organ Resistance
Plasma: low sodium, high pot
Urine: high sodium, low pot
Why does pituitary disease not affect aldosterone levels?
aldosterone not regulated by ACTH. It is regulated by the Renin-Angiotensin-Aldosterone system
Describe the RAA system?
Renin produced by kidneys in response to decreased renal BP.
Stimulates liver to produce angiotensin I
Lungs convert it to angiotensin II
Stimulate adrenals to release aldosterone
Aldosterone acts on kidneys
What enzyme converts cortisol into cortisone?
What can inhibit it?
What is the effect of its inhibition?
11beta-HSD2
Liquorice
Cortisol remains bound to receptor
Aldosterone cannot bind, so you get hypertension
