Online modules- adrenal Flashcards
Name the layers in the adrenal gland
Cortex
Medulla
Name the subdivisions of the cortex
Zona reticularis
Zona fasciculate
Zona glomerulosa
Connective tissue
What is secreted from the zona reticularis and what does it control?
Responsible for the Renin-angiotension-aldosterone control. Secretes aldosterone.
Also controlled by ACTH and secretes sex hormones.
What is secreted from the zona fasciculate and what does it control?
It is controlled by ACTH release from the anterior pituitary gland.
It controls release of glucocorticoids such as cortisol, cortisone and corticosterone.
Put the subdivisions of the adrenal gland into order starting with the deepest going to the most superficial
Medulla Zona reticularis Zona fasciculate Zona glomerulosa Connective tissue
What are mineralocorticoid hormones?
They are hormones responsible for control of water and salt balance.
Characteristics of steroid hormones
All derived from cholesterol.
Only synthesised when the cells producing them respond to stimuli
Not stored within the cell
Bound to proteins during transport giving them a slow response.
What hormones are secreted from the medulla
Adrenaline and nor-adrenaline.
Describe the precursors to forming adrenaline
Tyrosine is converted to dopamine. Dopamine is converted to either adrenaline or noradrenaline.
Where is adrenaline made?
Chromaffin cells.
Why does adrenaline have a short half life?
It is unbound when transported giving it a very short half life.
What stimulates aldosterone release?
Angiotensin II
How does angiotensin II stimulate aldosterone release?
Works by stimulating cell growth of the cells within the zona glomerulosa.
What does secretion of aldosterone do to the body?
It causes NaCl retention. This means that due to an osmotic gradient water is reabsorbed in the kidney. Pottasium is however lost due to the Na+K+ATPase.
What can cause renin release?
A decrease in blood pressure
A decrease in sodium chloride concentration
A decrease in extracellular volume.
What would happen if a patient has too much aldosterone?
Water retention therefore increased bp
Hypokalaemia due to pottasium being excreted a lot
Levels of sodium would be high
What is Conn’s syndrome?
A tumour in the zona glomerulosa causing aldosterone to be secreted.
Biochemical test results for Conns syndrome
Increased Na+
Increased water
Decreased K+
Symptoms of Conns syndrome
Hypertension
Hypokalaemia
Conns syndrome is the only disease causing more aldosterone to be released. T or F
F- another cause of excess aldosterone release is adrenal hyperplasia. Usually it occurs bilaterally.
Diagnostic tests for primary aldosteronism
Aldosterone to renin ratio (you would expect them to be proportional to one another considering renin ultimately causes aldosterone release.
If the ratio is greater than 750 then carry out a saline supression test. Give the patient 2L of saline solution over the period of 4 hours. You would expect their aldosterone to stop being released because the patient has plenty of salt and water, however in these conditions this wont occur. If the aldosterone levels fail to fall by 50% then it is primary aldosteronism.
Treatment of primary aldosteronism
If unilateral e.g. in Conns syndrome- surgery may be an option. The adenoma is removed laparoscopically.
If bilateral you cant remove both adrenal glands therefore should treat with aldosterone receptor antagonists e.g. spiranolactone that reduce the absorption of NaCl.
Name a treatment alternative to spiranolactone in bilateral hypersecretion of aldosterone
Eplerenone.
Where are glucocorticoids made and secreted from?
The zona fasciculate.
Main hormone produced by the zona fasciculate
Cortisol
What stimulates glucocorticoid hormones to be produced by the zona fasciculate?
ACTH- produced by the pituitary.
How does ACTH act on the zona fasciculate?
It increases growth of the cells so they can release more hormone.
Where does cortisol act around the body?
Fat tissue
Liver
Muscle
Other tissues (except for the brain)
What does cortisol do to fat tissue
Causes an increase in lipolysis
This causes increased free fatty acids
What does cortisol do to muscle tissue
Causes proteolysis
Increased plasma amino acids
What does cortisol do to the liver?
Increases gluconeogenesis. This causes an increase in circulating blood glucose.
What does cortisol do to other tissues (other than the brain)
Decreases glucose uptake
Contributes to a rise in blood glucose.
Why does cortisol have all these effects on the body?
It provides the body with energy sources when it is stressed.
It also increases the bodies responsiveness to adrenaline which helps to stop the body from going into shock.
Cortisol also has anti-inflammatory properties because it is a slight immunosupressant.
Biochemical and anatomical consequences of hypersecretion of cortisol
Muscle wasting due to proteolysis
Plasma fatty acids become centrally distributed around the body.
Increase in concentration of glucose
Macrophage activity and cytokine production are decreased.
Increase in adrenoceptors causes cardiac output and blood flow to increase.
Reduces osteoblast activity in the bones and decreases collagen formation.
Symptoms of hypersecretion of cortisol
MOON FACE- due to redistribution of fat.
Plethoric complexion- red ish colouration.
Cataracts due to build up of conjunctival oedema.
Proximal myopathy and muscle weakness
Easily bruised, recurrent skin infections, slow wound healing.
Thinning of skin
Central obesity
Typical presentation of patient with hypersecretion of cortisol.
Patient will present with either muscular weakness of back pain (due to rapid increase in weight).
Patient may notice themselves becoming thirsty and going to the toilet more (polydipsia and polyuria) due to increased blood glucose levels.
Patient may present with bone pain.
Insomnia is a common complaint.
Some patients present with feelings of euphoria and others with intense depression.
How is cortisol regulated?
The hypothalamus released CRH (corticotropin releasing hormone) which stimulates the anterior pituitary to release ACTH. ACTH stimulates the release of cortisol.
Cortisol then feeds back to the hypothalamus to stop the release of CRH.
Cushings disease
Hypersecretion of cortisol.
Causes of cortisol hypersecretion can either be
ACTH dependent
ACTH independent
Ectopic cancers
ACTH dependent description
Most common cause of Cushings disease. A tumour in the pituitary increases the production and secretion of ACTH.
Why doesn’t the negative feedback loop work for ACTH dependent cortisol secretion?
A tumour will always produce ACTH and will not be suppressed by high levels of cortisol as it would normally have been in a physiological gland.
What additional symptoms will patients have with ACTH dependent cortisol hypersecretion
Patient my experience headaches
Bitemporal hemioopnea (loss of peripheral vision)
Acromegaly.
Ectopic cancers description
Another form of ACTH dependent production of cortisol. Most commonly it is cancers from the lung, thymus and pancreas. They are responsible for secreting hormones that naturally occur in the body at an alarming rate.
ACTH independent
Cushings disease in this case does not come from hypersecretion of ACTH. It actually comes from an adrenal adenoma, adrenal carcinoma or nodular hyperplasia.
In these cases levels of ACTH will be low due to it being suppressed successfully by the high levels of cortisol.
Active tumours of the adrenal glands that secrete hormones are more likely to be
Adenomas rather than carcinomas.
What else is affected by increased ACTH secretion
The zona reticularis which secretes sex hormones. If cushings is present excess sex hormone will be released.
What is produced in large amounts due to ACTH secretion action on the zona reticularis
DHEA- a prohormone of sex steroid. Therefore producing large amounts of testosterone.
Women with high levels of DHEA may have
Acne
Amenorrhheoa
Frontal balding
Facial hair growth
Men with high levels of DHEA may present as
Also having acne
Libido (lack of sex drive)
Impotence (erectile dysfunction)
How would you diagnose cushings?
Low dose dexamethasone test- dexamethasone switches off your own production of cortisol. Test cortisol in the morning and see if it is suppressed.
Without cushings- less than 50.
Treatment of cushings disease
Stop the synthesis of the hormone by metyrapone
