Adrenal Glands Flashcards
What are the 2 components of the adrenal gland?
- Adrenal cortex.
- Adrenal medulla.
List the classes of steroid hormones synthesised and released from the adrenal cortex.
1 - Glucocorticoids.
2 - Mineralocorticoids.
3 - Adrenal androgens.
What class of hormones are synthesised and released from the adrenal medulla?
Catecholamines.
List the layers of the adrenal cortex from superficial to deep.
1 - Zona glomerulosa.
2 - Zona fasciculata.
3 - Zona reticularis.
What class of hormones are synthesised at the zona glomerulosa?
Mineralocorticoids.
What class of hormones are synthesised at the zona fasciculata?
Glucocorticoids.
What class of hormones are synthesised at the zona reticularis?
Androgens.
List 2 mineralocorticoids.
1 - Aldosterone.
2 - DOC.
Give an example of a glucocorticoid.
Cortisol.
List 2 adrenal androgens.
1 - DHEA.
2 - Androstenedione.
What is the precursor molecule steroidogenesis?
Cholesterol.
What is the name of the disease that causes an excess of glucocorticoids?
Cushing’s syndrome.
What is the name of the disease that causes an excess of mineralocorticoids?
Conn’s syndrome.
What is the name of the disease that causes an excess of adrenal androgens?
Hyperandrogenism.
What is the name of the disease that causes an excess of catecholamines?
Phaeochromocytoma (a tumour).
List 2 causes of excess adrenal activity.
1 - Adrenal tumours.
2 - Congenital adrenal hyperplasia.
Are steroid hormones lipophilic or hydrophilic?
Lipophilic.
What are permissive actions of drugs?
Actions that do not directly initiate but allow other actions to occur in the presence of other factors.
List 3 actions of glucocorticoids.
1 - Increase glucose mobilisation.
2 - Maintenance of circulation.
3 - Immunomodulation.
List 3 ways by which glucocorticoids increase glucose mobilisation.
1 - By augmenting gluconeogenesis.
2 - Via amino acid generation.
3 - By increasing lipolysis.
List 2 ways by which glucocorticoids maintain circulation.
1 - By maintaining vascular tone.
2 - By controlling the salt and water balance.
What is the role of glucocorticoids in immunomodulation?
Glucocorticoids dampen the immune response.
List the proteins that bind to glucocorticoids in the blood, and give the relative abundance of each.
- 90% of glucocorticoids are bound to corticosteroid-binding globulin (CBG).
- 5% bound to albumin.
- 5% free and bioavailable.
What is the effect of inflammation on corticosteroid-binding globulin (CBG)?
CBG decreases with inflammation.
Define diurnal.
Occurring during daylight hours.
Define circadian.
Occurring once every 24 hours.
When are the peaks of cortisol concentration during the day?
At 7 am and 3pm.
Define stress.
The sum of the body’s responses to adverse stimuli.
List 5 adverse stimuli that cause biological stress.
1 - Infection.
2 - Trauma (physical and psychological).
3 - Haemorrhage.
4 - Illness.
5 - Exercise.
What is the activity of DOC relative to aldosterone?
Doc has 3% activity of aldosterone.
What is the main function of mineralocorticoids?
To control salt and water balance.
List 5 sites of the body at which mineralocorticoids act.
1 - Kidneys.
2 - Colon.
3 - Pancreas.
4 - Salivary glands.
5 - Sweat glands.
What is the function of renin?
To increase blood pressure.
Describe the process by which mineralocorticoids are regulated.
1 - A decrease in renal perfusion pressure causes juxtaglomerular cells to release renin.
2 - Renin converts angiotensin into angiotensin I, which is then converted into angiotensin II.
3 - Angiotensin II stimulates the angiotensin II receptor to release aldosterone and to cause vasoconstriction.
4 - Aldosterone binds to mineralocorticoid receptors to promote sodium retention to further increase blood pressure.
What stimulates angiotensin production?
Vasoconstriction.
Where is angiotensin produced?
In the liver.
List 2 factors that increase renin release (excluding a decrease in renal perfusion pressure).
1 - β-adrenergic action.
2 - Presence of prostaglandins.
List 2 factors that decrease renin release.
1 - Presence of atrial natriuretic peptide.
2 - Presence of dopamine.
How do mineralocorticoids affect the pancreas, sweat glands, salivary glands and colon?
They increase sodium reabsorption.
List 2 functions of mineralocorticoids other than control of salt and water balance.
1 - Myocardial collagen production.
2 - Role in cardiac fibrosis / remodelling.
How do mineralocorticoid receptors promote sodium retention?
By increasing the transcription of apical Na channels and Na/K pumps.
For which molecules do mineralocorticoids have an affinity?
1 - Mineralocorticoids (e.g. aldosterone).
2 - Cortisol! (receptors have a low specificity).
Why aren’t mineralocorticoid receptors inundated by cortisol?
Cortisol is converted into cortisone by 11β-hydroxysteroid dehydrogenase, for which the receptors do not have an affinity. This occurs before it is able to reach the receptor.
Why might ingestion of liquorice result in an increase in blood pressure?
Liquorice inhibits the activity of 11β-hydroxysteroid dehydrogenase, allowing cortisol to reach and bind to the mineralocorticoid receptor.
Where are androgens produced outside of the adrenal gland?
1 - Ovaries.
2 - Testes.
3 - Adipose tissue.
How are adrenal androgens different from androgens produced elsewhere?
Adrenal androgens are weaker.
What is the function of adrenal androgens that is specific to postmenopausal women?
Adrenal androgens are oestrogen precursors in postmenopausal women.
- Postmenopausal women no longer produce oestrogen at the ovaries.
What regulates the production of adrenal androgens?
By ACTH.
What regulates the production of non-adrenal androgens?
By gonadotropins.
List 3 functions of androgens.
1 - Puberty initiation.
2 - Hair growth.
3 - Sexual interest.
What is the predominant cell type of the adrenal medulla?
Sympathetic ganglia.
What type of fibres supply the ganglia of the adrenal medulla?
Sympathetic pre-ganglionic neurones.
What neurotransmitter is used to stimulate the ganglia of the adrenal medulla?
Acetylcholine.
What do the ganglia of the adrenal medulla synthesise?
Catecholamines.
List 3 catecholamines.
1 - Adrenaline.
2 - Noradrenaline.
3 - Dopamine.
Which enzyme is necessary for the conversion of noradrenaline into adrenaline?
Phenylethanolamine-N-methyltransferase.
How do the products of the ganglia of the adrenal medulla enter the blood?
They diffuse directly into adrenal capillaries.
Describe the relative amounts of catecholamines produced by the adrenal medulla.
- 80% of catecholamines produced is adrenaline.
- 20% of catecholamines produced is noradrenaline.
- Dopamine is produced in trace amounts.
Give an example of a permissive effect of cortisol.
High cortisol levels are necessary for normal catecholamine synthesis.
What is the precursor for catecholamine synthesis?
Tyrosine.
To which receptors to catecholamines bind?
Adrenergic receptors.
What is the effect of alpha adrenergic receptor stimulation?
Vasoconstriction.
What is the main effect of β1 adrenergic receptor stimulation?
To increase cardiac output.
What is the main effect of β2 adrenergic receptor stimulation?
Smooth muscle relaxation in the bladder, uterus and bronchioles.
List 2 effects of β3 adrenergic receptor stimulation.
1 - Regulation of lipolysis.
2 - Regulation of thermogenesis.
What is the general function of catecholamines?
To stimulate fight or flight responses (via the sympathetic nervous system).
List 2 examples of adrenal tumours.
1 - Adrenal incidentaloma.
2 - Adrenocortical carcinoma.
