Adrenals Flashcards
What is the role of cortisol?
Inhibits the immune system Inhibits bone formation Raises blood glucose Increases metabolism Increases alertness
How is cortisol released?
The hypothalamus releases corticotrophin release hormone (CRH)
Stimulates the anterior pituitary to release adrenocorticotrophic hormone (ACTH).
Stimulates the adrenal gland to release cortisol
What is Cushing’s disease?
Prolonged abnormal elevation of cortisol Pituitary adenoma (tumour) secretes excessive ACTH
Features of Cushing’s
Round “moon” face Central Obesity Abdominal striae Buffalo Hump (fat pad on upper back) Proximal limb muscle wasting Hypertension Cardiac hypertrophy Hyperglycaemia (Type 2 Diabetes) Depression Insomnia Osteoporosis Easy bruising and poor skin healing
What are the causes of Cushing’s syndrome?
Exogenous steroids (in patients on long term high dose steroid medications)
Cushing’s Disease (a pituitary adenoma releasing excessive ACTH)
Adrenal Adenoma (a hormone secreting adrenal tumour)
Paraneoplastic Cushing’s
How do you test for Cushing’s syndrome?
Dexamethasone suppression test
Low dose test initially
High dose test if Low dose test is abnormal (high/normal cortisol)
What happens in low dose dexamethasone test?
1mg Dex given 10pm at night
Cortisol measured 9am next day
Dexamethasone suppresses the release of cortisol by effecting negative feedback
Hypothalamus reduces CRH output
Pituitary reduces ACTH output
Results in a low cortisol level
Abnormal when cortisol is not suppressed - Cushing’s Syndrome
What happens in high dose dexamethasone test?
8mg Dexamethasone given 10pm at night
Cortisol measured 9am next day
In Cushing’s Disease - still some response to negative feedback, 8mg suppresses cortisol
In adrenal adenoma, cortisol production is independent from the pituitary
Cortisol is not suppressed,ACTH is due to negative feedback
In ectopic ACTH, neither cortisol or ACTH will be suppressed
ACTH production is independent of the hypothalamus or pituitary gland
What test is used alternatively to dexamethasone test?
24 hour urinary free cortisol
Does not indicate the underlying cause
What is Addisons?
AKA Primary Adrenal Insufficiency
Reduction/lack of secretion of cortisol and aldosterone
What is Secondary Adrenal Insufficiency?
Inadequate ACTH stimulating the adrenal glands, resulting in low cortisol release
Result of loss or damage to the pituitary gland
Can be due to surgery to remove a pituitary tumour, infection, loss of blood flow or radiotherapy
What is Tertiary Adrenal Insufficiency?
Inadequate CRH release
Usually due to long term oral steroids (for more than 3 weeks) causing suppression of the hypothalamus
Long term steroids should be tapered slowly to allow time for the adrenal axis to regain normal function
What are the symptoms of adrenal insufficiency?
Fatigue Nausea Cramps Abdominal pain Reduced libido
What are the signs of adrenal insufficiency?
Bronze hyperpigmentation to skin (ACTH stimulates melanocytes to produce melanin)
Hypotension (particularly postural hypotension)
Hyponatraemia (Sometimes the only presenting feature)
Hyperkalaemia
Investigations for adrenal insufficiency?
Short synacthen test is the test of choice to diagnose adrenal insufficiency
What antibodies are present in 80% of autoimmune adrenal insufficiency?
Adrenal cortex antibodies
21-hydroxylase antibodies
What is short synacthen test?
Give synacthen - synthetic ACTH (ideally in morning)
Blood cortisol is measured at baseline, 30 and 60 minutes after administration
A failure of cortisol to rise (less than double the baseline) indicates primary adrenal insufficiency (Addison’s disease)
What is the treatment for Addison’s?
Hydrocortisone used to replace cortisol
Fludrocortisone used to replace aldosterone
Doses are doubled during an acute illness until they have recovered to match the normal steroid response to illness
What is Addisonian Crisis?
Acute presentation of severe Addisons
Reduced consciousness
Hypotension
Hypoglycaemia, hyponatraemia, hyperkaemia
Patients can be very unwell
Can be the first presentation of Addisons Disease or triggered by infection, trauma or other acute illness
What is the treatment for Addisonian Crisis?
Intensive monitoring if unwell
Parenteral steroids (i.e. IV hydrocortisone 100mg stat then 100mg every 6 hours)
IV fluid resuscitation
Correct hypoglycaemia
Careful monitoring of electrolytes and fluid balance
Treatment of hyperaldosteronism
Surgical removal of adenoma
Percutaneous renal artery angioplasty via the femoral artery to treat in renal artery stenosis
Effects of hyperaldosteronism
Blood pressure (hypertension) Serum electrolytes (hypokalaemia) Blood gas analysis (alkalosis)
Investigations for hyperaldosteronism
Renin and aldosterone levels
Calculate a renin / aldosterone ratio
CT / MRI to look for an adrenal tumour
Renal doppler ultrasound, CT angiogram or MRA for renal artery stenosis or obstruction
Causes of Secondary hyperaldosteronism
Renal artery stenosis
Renal artery obstruction
Heart failure
What is secondary hyperaldosteronism?
Excessive renin stimulating the adrenal glands to produce more aldosterone
Serum renin will be high
Occurs when the blood pressure in the kidneys is disproportionately lower than the blood pressure in the rest of the body
Causes of primary hyperaldosteronism
An adrenal adenoma secreting aldosterone (most common) Bilateral adrenal hyperplasia Familial hyperaldosteronism type 1 and type 2 (rare) Adrenal carcinoma (rare)
What is primary hyperaldosteronism?
(Conn’s Syndrome)
Adrenal glands are directly responsible for producing too much aldosterone
Serum Renin is low due to high BP
What is the function of aldosterone?
Increase sodium reabsorption from the distal tubule
Increase potassium secretion from the distal tubule
Increase hydrogen secretion from the collecting ducts
What is phaeochromocytoma?
Tumour of the chromaffin cells that secretes unregulated and excessive amounts of adrenaline
How is the tumour pattern described in pheaochromocythoma?
The rule of 10
10% bilateral
10% cancerous
10% outside the adrenal gland
How to diagnose pheaochromocytoma
24 hour urine catecholamines
Plasma free metanephrines (less prone to dramatic fluctuations and a more reliable diagnostic tool)
Presentation of pheaochromocytoma
Anxiety Sweating Headache Hypertension Palpitations, tachycardia and paroxysmal atrial fibrillation
What is the management of pheochromocytoma?
Alpha blockers (i.e. phenoxybenzamine) Beta blockers once established on alpha blockers Adrenalectomy to remove tumour is the definitive management
