Adrenal - Basic Science & Hyperfunction Flashcards
What 3 things are produced in the adrenal cortex?
Glucocorticoids, mineralocorticoids and androgens
What is the main glucocorticoid hormone produced by the adrenal cortex?
Cortisol
What is the main mineralocorticoid hormone produced by the adrenal cortex?
Aldosterone
What type of cells are found in the adrenal medulla?
Chromaffin cells
What is produced by the adrenal medulla? Give two examples.
Catecholamines e.g. adrenaline and noradrenaline
The synthesis of all the corticosteroids in the adrenal cortex begins with what?
Cholesterol
Which type of steroid hormone is produced in the zona glomerulosa of the adrenal cortex?
Mineralocorticoids
What regulates mineralocorticoid activity?
Angiotensin II (RAAS) and K+ level
Which type of steroid hormone is produced in the zona fasciculata of the adrenal cortex?
Glucocorticoids
Which type of steroid hormone is produced in the zona reticularis of the adrenal cortex?
Androgens
What regulates glucocorticoid activity?
ACTH
What regulates androgen activity?
ACTH
What hormone is released from the hypothalamus in the hypothalamic-pituitary-adrenal axis?
Corticotropin releasing hormone
What hormone is released from the pituitary gland in the hypothalamic-pituitary-adrenal axis?
ACTH
RAAS is a major regulator of aldosterone production. It is activated in response to what?
Decreased blood pressure
What is the effect of aldosterone?
Increase sodium reabsorption, and increase hydrogen and potassium excretion
Are corticosteroid receptors intra or extracellular?
Intracellular
What is the name for the clinical state of chronic glucocorticoid excess?
Cushing’s syndrome
When is cortisol usually at its highest and lowest levels in the normal circadian rhythm?
Usually lowest at midnight and highest upon waking
What is the most common cause of Cushing’s syndrome?
Use of oral steroids
What is the most common endogenous cause of Cushing’s syndrome?
Cushing’s disease (ACTH secreting pituitary adenoma)
What are the two main ACTH dependent (high ACTH) causes of Cushing’s syndrome?
Cushing’s disease and ectopic ACTH production
What are the two main ACTH independent (low ACTH) causes of Cushing’s syndrome?
Adrenal pathology (adenoma/hyperplasia) and iatrogenic steroid use
What effect does Cushing’s syndrome have on blood pressure?
Hypertension
What effect does Cushing’s syndrome have on blood glucose levels?
Hyperglycaemia
If individuals with Cushing’s syndrome have an acid-base disorder, what is this most likely to be?
Hypokalaemic metabolic alkalosis
What is the first line screening test for Cushing’s syndrome?
Overnight dexamethasone suppression test
In the overnight dexamethasone suppression test, 1mg of dexamethasone is given at midnight and a cortisol level is taken at 8am. If the individual has Cushing’s syndrome, the cortisol level will be greater than what?
50nmol/L
If an overnight dexamethasone suppression test is not suitable, what is another screening test that can be used for Cushing’s syndrome?
24h urinary free cortisol
A normal 24h urinary free cortisol would be less than what value?
280nmol/L
Once a screening test has confirmed Cushing’s syndrome, what investigation should be done next to determine between ACTH dependent and independent causes?
9am and midnight plasma ACTH and cortisol
What is the first line diagnostic test for Cushing’s syndrome?
48h low dose dexamethasone suppression test
How much dexamethasone is given every 6 hours in the low and high dose dexamethasone suppression tests?
Low = 0.5mg / high = 2mg
When performing 48h dexamethasone suppression tests, when should plasma cortisol levels be measured?
At time 0, and 6 hours after the last dose
In individuals with Cushing’s syndrome, in the 48h low dose dexamethasone suppression test, plasma cortisol levels will be greater than what 6 hours after the last dose?
50nmol/L
What is the advantage of the 48h high dose dexamethasone suppression test over the low dose version?
High dose can differentiate between pituitary and non-pituitary causes of Cushing’s syndrome
If cortisol is suppressed after the 48h high dose dexamethasone suppression test, this suggests that the pathology is where?
Pituitary gland
If cortisol is not suppressed after the 48h high dose dexamethasone suppression test, this suggests that the pathology is where?
Adrenal gland or ectopic
If ACTH levels are low in someone with Cushing’s syndrome, what is the first line imaging investigation?
Adrenal CT
If ACTH levels are low in someone with Cushing’s syndrome but there is no mass on adrenal CT, what investigations could be tried next?
Adrenal vein sampling or adrenal scintigraphy
If tests indicate that Cushing’s syndrome is likely of pituitary origin, what imaging investigation should be considered?
Pituitary MRI
If tests indicate that Cushing’s syndrome is likely of ectopic origin, what imaging investigation should be considered?
Contrast CT chest/abdo/pelvis
If corticotropin releasing hormone causes cortisol to rise in someone with Cushing’s syndrome, the underlying cause is most likely what?
Pituitary adenoma (Cushing’s disease)
If corticotropin releasing hormone doesn’t cause cortisol to rise in someone with Cushing’s syndrome, then the underlying cause is most likely what?
Ectopic ACTH production
How should Cushing’s syndrome caused by a pituitary adenoma be treated?
Trans-sphenoidal surgical removal of the adenoma
How should Cushing’s syndrome caused by an adrenal adenoma be treated?
Adrenalectomy
Untreated Cushing’s syndrome has increased mortality because of what?
Increased risk of vascular disease
Pseudo-Cushing’s syndrome is most commonly caused by one of what two things?
Alcohol excess or severe depression
What are the 3 main features of primary hyperaldosteronism?
Hypertension, hypokalaemia, alkalosis
What are the two main causes of primary hyperaldosteronism?
Adrenal adenoma (Conn’s syndrome) or adrenal hyperplasia
What is the first line investigation for primary hyperaldosteronism?
Plasma aldosterone to renin ratio
What happens to aldosterone and renin levels in primary hyperaldosteronism?
Raised aldosterone, low renin
Once a plasma aldosterone to renin ratio has confirmed primary hyperaldosteronism, what further investigations should be performed to identify the underlying cause?
CT abdomen and adrenal vein sampling
How is primary hyperaldosteronism caused by Conn’s syndrome treated?
Adrenalectomy
How is primary hyperaldosteronism caused by adrenocortical hyperplasia treated?
Potassium sparing diuretic e.g. spironolactone
What causes secondary hyperaldosteronism?
High renin levels as a result of low renal blood flow
