Adrenal Gland Flashcards
In order what are the layers of the adrenal gland?
- Capsule
- Cortex
- Adrenal medulla
What are the three layers of the adrenal cortex (in order)?
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
What does the zona glomerulosa produce?
Mineralcorticoids e.g aldosterone
What does the zona fasciculata produce?
Glucocorticoids e.g cortisol
What does the zona reticularis produce?
Androgens e.g DHEA
What does the adrenal medulla produce?
Norepinephrine and epinephrine
What are the functions of aldosterone?
- Aldosterone increases uptake of sodium by the kidneys so less is lost in the urine. This leads to more water staying in the body.
- –> increasing blood volume therefore increasing blood pressure. - Aldosterone promotes the loss of H+ in the urine, therefore helping to prevent acidosis.
What controls aldosterone secretion?
The RAAS pathway
Where is renin secreted from?
JGA in the kidneys
Where is angiotensinogen produced?
The liver
Explain the RAAS system.
- Renin is produced by the kidneys in response to decreased blood pressure.
- Renin travels to the liver where it converts angiotensinogen into angiotensin 1.
- Angiotensin 1 travels in the blood to the lungs.
- ACE is present in the lungs and converts angiotensin 1 into angiotensin 2.
- Angiotensin 2 causes vasoconstriction and stimulates aldosterone production in the adrenal gland.
Where does angiotensin II act?
The smooth muscle in the walls of arterioles.
Where are glucocorticoids produced?
The zona fasciculata in the adrenal gland
What are the effects of glucocorticoids?
- Protein breakdown
- Gluconeogenesis
- Lipolysis
- Resistance to stress
- Increased blood pressure
- Anti-inflammatory effects
- Depression of immune responses
What is the function of protein breakdown by cortisol?
Cortisol breaks down the proteins in muscle fibres increasing the number of amino acids in the blood, allowing new protein production.
How does cortisol combat stress?
Increases blood glucose levels therefore there is more ATP available to combat stress.
How does cortisol increase blood pressure?
Cortisol makes blood vessels more sensitive to hormones that cause vasoconstriction, thus increasing blood pressure.
—> Important in cases of severe blood loss.
How do glucocorticoids have an anti-inflammatory effect?
Glucocorticoids inhibit white blood cells that participate in the inflammatory response.
However this also delays tissue repair slowing wound healing.
—> Useful in treating chronic inflammatory conditions such as rheumatoid arthritis.
What is the importance of depressed immune response induced by glucocorticoids?
Glucocorticoids are prescribed after organ transplant to delay tissue rejection.
Explain the control of cortisol secretion.
- CRH produced by hypothalamus
- Goes to AP through HPS
- Corticotrophs in AP secrete ACTH
- ACTH acts on the adrenal cortex stimulating cortisol production.
Where are androgens such as DHEA secreted?
The zona reticularis in the adrenal cortex
What is the main androgen secreted by the zona reticularis?
DHEA
What does DHEA do in men?
Stimulates the production of testosterone
What does DHEA do in women?
- DHEA is converted into oestrogen
- Increases libido
- Growth of pubic hair
Note: after menopause the only source of oestrogen for women comes from DHEA.
What controls DHEA secretion?
ACTH
Where does epinephrine it’s greatest effect?
The heart
Where does noepinephrine have it’s greatest effect?
Blood vessels
What cells secrete epinephrine and norepinephrine?
Chromaffin cells in the adrenal medulla
How is secretion of epinephrine and norepinephrine by chromaffin cells controlled?
Chromaffin cells are innervated by preganglionic cells of the ANS.
This means the ANS has direct control over chromaffin cells and thus hormone release can occur very quickly.
What are the main actions of norepinephrine and epinephrine?
- Causes the fight or flight response, increasing heart rate and force of contraction.
- Increased blood pressure
- Increased blood flow the liver, heart, skeletal muscle and adipose tissue.
- Dilates the airway to the lungs
- Increased levels of glucose and fatty acids in the blood.
What type of molecule is norepinephrine?
Neurotransmitter
What type of molecule is epinephrine?
Hormone
When is norepinephrine used?
To raise heart rate and modulate blood pressure
When is epinephrine used?
Used as an effective antihistamine in the treatment of shock.
What is Conn’s syndrome?
High levels of aldosterone in the blood compared to renin.
What is Conn’s syndrome often caused by?
Lesion on the adrenal cortex
How is Conn’s syndrome diagnosed?
CT/MRI scan
What are the symptoms of Conn’s syndrome?
Hypertension
Hyperatremia
Hypokalaemia
What is Cushing’s syndrome?
The production of excess cortisol, often due to the excess production of ACTH.
What often causes Cushing’s syndrome?
A pituitary tumour
What are the usual treatments for Cushing’s?
Surgery, radiation, chemotherapy
What are the clinical features of Cushing’s?
Moon face (excessive fat around the face) Hypertension
How do you diagnose Cushing’s?
Urine test for cortisol levels at midnight.
What is Addison’s disease?
Deficiency of cortisol
What can cause Addison’s disease?
Autoimmune destruction of the adrenal gland.
- –> Secondary cause can be a lack of ACTH production by the anterior pituitary
- –> Use of steroids
What are the clinical features of Addison’s disease?
Anorexia Strange skin pigmentation Dizziness Hypotension Hypoglycaemia
How is Addison’s disease diagnosed?
Testing for: Hyponatremia Hyperkalaemia Low cortisol levels in the morning CT of adrenal gland MRI of pituitary
What is the treatment for Addison’s disease?
Hydrocorticosone
What is the dexamethasone suppression test?
The overnight dexamethasone suppression test involves taking a dose of a corticosteroid medicine called dexamethasone to see how it affects the level of a hormone called cortisol in the blood. This test checks for Cushing’s syndrome. In this condition, large amounts of cortisol are produced by the adrenal glands.
Cortisol level should decrease after you receive dexamethasone. Low dose: Overnight – 8 a.m. plasma cortisol lower than 1.8 micrograms per deciliter (mcg/dL) or 50 nanomoles per liter (nmol/L) Standard – Urinary free cortisol on day 3 lower than 10 micrograms per day (mcg/day) or 280 nmol/L.
What is the synacthen test?
A synacthen test tests for Addison’s disease.
It involves stimulating the adrenal glands and then checking to see if they respond.
