6. Hyperadrenal disorders Flashcards
Features of Cushing’s Syndrome
Caused by having too much cortisol
- Can be caused by a tumour in the pituitary that’s making ACTH
- Can also rarely be due to a benign tumour of the adrenal gland
- Cortisol switches protein synthesis off and fat syntheisis on
- Get bruising because proteins for healing arent available
- Get fat deposition- ‘moon face’ and ‘buffalo hump’
- Stretch marks- putting on a lot of fat quickly
- Weaker
Clinical features of Cushing’s
- Too much cortisol
- Centripedal obesity
- Moon face and buffalo hump
- proximal myopathy
- Hypertension and hypokalaemia- due to cortisol binding to receptors in the kidney (retain Na+ and K+)
- red striae, thin skin and easy bruising
- Osteoperosis, diabetes
Causes of Cushing’s
Can be EXOGENOUS or ENDOGENOUS:
Exogenous:
- Taking too many steroids by mouth: cortisol type steroid cause loss of protein and more fat- glucocortisoid over use is more common cause than tumour. BUT bodybuiling steroids (testosterone) causes opposite effects
Endogenous:
- Pituitary dependant Cushing’s disease
- Ectopic ACTH from cancer
- Adrenal adenoma making cortisol
THREE tests to determine the cause of Cushing’s disease
- 24 hour urine collection for urinary free cortisol
- Blood diurnal cortisol levels
- Low dose dexamethasone suppression test (gold standard)- will have high levels of cortisl after suppression
Dangers of undiagnosed Cushing’s disease
Patients can become immunocompromised since they can’t heal and synthasise proteins- develop sepsis
Problems with cortisol measurement
Cortisol is high in the morning and low when you go to sleep- diurnal- stress of blood test is another confounding factor
- To overcome this we do a 24 hour urine collection for urinary free cortisol
People with cushing’s loose their diurnal rythm and have high cortisol at all times
Low dose demaxamethasone suppression test
Dexamethasone is an artificial steroid
You take a blood test before giving it, then you give the dexamethasone and at the end of that, normal people will have ZERO cortisol (because you don’t need more steroid) the pituitary will not produce ACTH since the system is saturated with steroid
People with cushing’s will still have high cortisol
- 0.5mg, 6 hourly for 48 hours
Treatment of cushing’s (dependant for each cause)
- Pituitary surgery (transphenoidal hypophysectomy)
- Bilateral adrenalectomy (removal of both adrenal glands to prevent further cortisol production)
- Unilateral adrenalectomy for adrenal mass (adrenal lump in one gland)
ALL treatments are proceeded by use of ALPHA blockers- this is because high blood pressure is an urgent issue due to VASONSTRICTION
Pheneochromocytoma
A tumour of the adrenal medulla that leads to the production of loads of catecholamines
Metrapyone mechanism of action
Inhibits 11b-hydroxylase
This slows down the cortisol synthesis pathway and thus can be used as a tretament for Cushing’s
Reduces production of cortisol and corticosterone
No negative feedback by 11-deoxycortisone so ACTH accumulates
Uses of metrapyone
- Control of Cushing’s syndrome prior to surgery- patients are not good surgery candidates since they are predisposed to urgery wit thin skin (dose is according to serum cholesterol- should be between 150-300 nmol/L)
- Control of Cushing’s after radiotherapy
Metrapyone effect on aldosterone production
11B-Hydroxylase (inhibited by metrapyone) is also relevant in the aldosterone production- converts 11-deoxycorticosterone to corticosterone
Inhibition leads to accumulation of 11-deoxycorticosterone and 11-deoxycortisone
These have mineralocorticoid properties- acts like aldosterone
causes salt retention and hypertension so cant use it long term
Effect of metyrapone on sex steroid production
Since metyrapone blocks two arms of the pathway it funnels all production towards sex steroid synthesis
It causes an increase in adrenal androgens- can cause hirtuism
Ketoconazole mechanism of action
Inhibits cytochrome P450 SCC (side chain cleavage) enzymes, thus blocking the production of glucocorticoids, mineralocorticoids and sex steroids
Uses and unwanted actions of Ketoconazole
Uses: Cushings syndrome treatment and control of symptoms prior to surgery (orally active)
Unwanted actions:
- Nausea, vomiting, abdominal pain
- Alopecia
- Liver damage (could be fatal)
- Ventricular tachycardias
- Gnaecomastia, oligospermia, impotence
Conns syndrome characteristics
Benign adrenocorticol tumour in the zona glomerulosa makes aldosterone in excess
Causes patients to retain sodium and lose potassium
HYPOTENSION and HYPOKALAEMIA
Diagnosis of Conn’s syndrome
To identify primary hyperaldesteronism:
- If the patient has high blood pressure and low potassium levels on blood test
To identify Phyperaldo specific to Conn’s:
- Measure the aldosterone, if it is high, measure the renin, this should be supressed by the excess aldosterone
Conns syndrome treatment
Medicine use, removal of tumour
to stop the effects of excess aldosterone you give mineralocorticoid receptor antagonist- SPIRINALACTONE
Spironolactone mechanism
Converted to several active metabolites including CANRENONE, a competative antagonist of the mineralocorticoid receptor
Na+ reabsorption and K+ excretion in the kidney tubules
It is a potassium sparing diuretic
With bilateral adrenal hyperplasia, you may need to remove both adrenals (but dont want to do this to preserve cortisol production) In this case you use long term spirinalactone
Unwanted actions of spirinalactone
Spirinalactone is a very non-specific so there are lots of side-effects;
- Causes menstrual irregularities (progesterone receptor antagonist)
- Causes gynaecomastia in men (androgen receptor antagonist)
- GI tract iritation
Eplerenone effect
- Also a MINERALOCORTICOID RECEPTOR ANTAGONIST
- Has fewer side-effects than spironolactone so used more frequently
- More specific so interferes less with progesterone and androgen receptors
- MORE LIKELY TO BE USED LONG TERM
Characteristics of phaechromoctoma
Tumours of the adrenal medulla which secrete catecholamines (adrenaline and noradrenaline)
Adrenaline gives you a rapid effect- causes a massive rise in blood pressure (300/150)
Causes sudden onset of panic, anxiousness, tachycardia and hypertension
Clinical features of phaechromocytoma
If you see episodic severe hypertension in young people, phaeochromocytoma is a possibility
Could result in VENTRICULAR FIBRILLATION
Built up release could be tiggered after abdominal palpation or if there is a trauma
can cause myocardial infarction or stroke
Can also cause sudden cardiac death so is a medical emergency
Management of Phaeochromocytoma
Eventually need surgery, but also requires careful preparation to prevent a hypertensive crisis which can be triggered by anaesthetic
First give an alpha blocker (May have to give IV fuids)
Now give beta blockade to prevent tachycardia
