Endocrinology 8 - The Adrenals and Corticosteroids Flashcards
Describe the circulation of the adrenal gland
- Left adrenal vein drains into the renal vein
- Right adrenal vein runs into the inferior vena cava
Describe the anatomy of the adrenal gland.
- Adrenal medulla is in the middle
- Adrenal cortex is the outside. There are three layers, the zona glomerulosa, zonafasciculata and zona reticularis (starting from outside)
- Encased in a capsule
Where are catecholamines made?
The adrenal medulla, in the chromaffin cells
Where are corticosteroids made?
In the adrenal cortex
What is a tributary vein?
A vein that enters into a larger vein
Give some examples of catecholamines
- Adrenaline
- Noradrenaline (dopamine)
Give some examples of corticosteroids
- Mineralocorticoids, such as aldosterone
- Glucocorticoids, such as cortisol
Where is aldosterone made?
Zona glomerulosa
Where is cortisol made (alongside some androgens and oestrogens)?
- Zona fasiculata makes cortisol
- Zona reticularis makes androgens
What proportion of aldosterone is unbound, bound to CBG and bound to albumin?
40% unbound
15% bound to CBG
45% bound to albumin
What proportion of cortisol is unbound, bound to CBG and bound to albumin?
10% unbound
80% bound to CBG
10% bound to albumin
How much higher is the concentration of cortisol than that of aldosterone?
1000 fold difference, cortisol is highest at night
Which receptors can cortisol bind to?
- Glucocorticoid receptors
- Aldosterone receptors
Which receptors can aldosterone bind to?
Aldosterone receptors
How does aldosterone regulate cortisol?
- Cortisol is converted to cortisone via 11bHSD2
- Cells that produce this enzyme are protected from cortisol, only aldosterone can bind to the receptors.
- This is present in the kidney and placenta (as cortisol would inhibit growth of the foetus)
Describe how the renin-angiotensin-aldosterone system works.
- Sympathetic nerves, low blood pressure, and macular densa cells (low sodium ion concentration) increase renin production from granular cells.
- Renin increases sodium reabsorption and therefore water follows and blood pressure is reduced
- Renin acts on a angiotensin (liver and lungs) making aldosterone
- Aldosterone increases sodium channel expression
Describe the mechanism of action of aldosterone
- Sodium channel expression in the distal tubule increases and the sodium potassium pump returns the sodium into the blood.
- Water follows as a result
What is the optimal level of cortisol?
- All MR occupied and some GR
- High ratio
- Occurs in stress, and in the morning
List the actions of cortisol in metabolism
- Increases glucogeneisis, making glucose readily available, and glycogenesis.
- Reduces blood flow and GLUT 4 expression in skeletal muscle
- Prevents storage of fatty acids in adipose
List the actions of cortisol in memory
- Serotonin promotes memory formation.
- Cortisol increases serotonin production so in times of stress we learn and don’t repeat our mistakes
List the supra-physiological actions of cortisol (when at higher levels than normal)
- Antiinflammatory and immunosupressive, so stress makes us more susceptible to disease
- Increased by alcohol and caffeine
- Chronically high can reduce memory
