The Adrenal Gland - Clinical Flashcards
Describe the hypothalamo-pituitary adrenal axis
CRH (corticotrophin releasing hormone) is produced by the anterior pituitary and stimulates ACTH (adrenocorticotrophic hormone) production
ACTH stimulates cortisol production in the adrenal cortex
What things can cause Addison’s disease?
Immune destruction Invasion Infiltration Infection Infarction Iatrogenic
What is Addison’s disease?
Primary adrenal insufficiency
What is the commonest cause of Addison’s?
Autoimmune destruction leading to lymphocytic infiltration of the cortex
What conditions are associated with autoimmune Addison’s?
Thyroid disease
T1DM
Premature ovarian failure
What antibodies are found in 70% of Addison’s patients?
Antibodies to 21-OHase
What symptoms are associated with addisons?
Weakness, fatigue, anorexia, wt loss Skin pigmentation or vitiligo Hypotension Unexplained vomiting/diarrhoea Salt craving Postural symptoms
What things may point towards adrenal failure as a diagnosis?
Unexplained hypoglycaemia
Other endocrine features, e.g. hypothyroidism, body hair loss, amenorrhoea
Previous depression, wt loss
What tests should you do in suspected adrenal insufficiency?
UE, glucose, FBC
Random cortisol
Synacthen test and basal ACTH
If a patient is really unwell with suspected adrenal insufficiency what tests should you do?
Treat with steroids first and do test later
What random cortisol is definitely not Addison’s?
> 700nmol/l
What random cortisol may be Addison’s?
<700nmol/l
How do you carry out a short synacthen test?
Take blood for cortisol and ACTH
Give 250microg tetracosactrin IM
Half an hour later take cortisol level
Half an hour after than take another cortisol level
If congenital adrenal hyperplasia suspected can analyse bloods for 17-OH progesterone to exclude 17-hydroxylase deficiency
When should a short synacthen be done?
0900h
What would you expect as a normal response to the short synacthen test?
Stimulated plasma cortisol >550nmol/l
Failure to meet this indicates adrenal insufficiency
How can you distinguish between secondary and primary adrenocortical insufficiency?
If ACTH supressed - 2ndary
If ACTH elevated - primary
What medication is given to treat Addison’s?
Glucocorticoids: Hydrocortisone 20-30mg or Prednisolone 7.5mg or Dexamethasone 0.75mg
Given in divided doses to mimic natural diurnal variation
Mineralocorticoids:
Fludrocortisone 50-300mg
What receptors does fludrocortisone bind to?
Aldosterone
How should you adjust the dose of fludrocortisone?
Based on clinical status, e.g. postural BP, oedema
UE
Plasma renin level
Certain patients when they are undergoing stress may need extra steroids - what groups of people might these be?
Hypoadrenal patients on replacement steroids
Patients on steroids in doses sufficient to suppress the pituitary adrenal axis (>7.5mg predn daily)
Patients who have received treatment in last 18m whose HPA may still be suppressed
If someone with Addisons is undergoing minor short lived stress/illness what advice should you give them re. their medications?
Double glucocorticoid dose
If someone with Addisons is undergoing major illness/operation what steroid replacement do they need?
100mg hydrocortisone IV stat
50-100mg HC IV 8hrly
As stress abates, reduce HC by 50% per day until back on usual replacement dose
What are the 3 most important rules for patients on steroids?
Never miss steroid doses
Double hydrocortisone in times of illness
If severe vomiting/diarrhoea call for help without delay - likely to need IM HC
What are endocrine causes of hypertension?
Unilateral adrenal adenoma Bilateral adrenal hyperplasia Phaeochromocytoma Cushing's syndrome Acromegaly Hyperparathyroidism Hypothyroidism Congenital adrenal hyperplasia
How can cushing’s syndrome cause hypertension and heart failure?
Xs cortisol –> sodium retention
What are the symptoms of cushing’s syndrome?
Central obesity HTN Glucose intolerance Hirsutism Amenorrhoea or impotency Purple striae Plethoric faces Easy bruising Osteoporosis Personality changes Acne Oedema Headache Poor wound healing
What are the causes of cushing’s syndrome?
Pituitary tumour (cushing's disease) Ectopic ACTH secretion, e.g. lung cancer
Adrenal tumour
Corticosteroid therapy
How do you screen for Cushing’s?
24h urinary free cortisol
1mg overnight dexamethasone suppression test taken at midnight
What is a normal 24hr urinary free cortisol?
14-135nmol/24h
What is a normal 1mg overnight dexamethasone suppression test?
<50nml/l but there will be no suppression in cushings
What is the first line localisation test for hypercortisolism?
9am and midnight plasma ACTH and cortisol
If ACTH not supressed adrenal cause unlikely
What other two tests can be used to localise in hypercortisolism?
Low and high dose dexamethasone suppression test
Not supressed by low dose dexamethasone =
Cushings due to corticosteroid therapy
Not suppressed by low dose, but supressed by high dose dexamethasone = ?
Cushing’s disease
Not supressed by high or low dose dexamethasone = ?
Ectopic ACTH secretion likely
In hypercorticolism, how can you differentiate between pituitary and ectopic ACTH secretion?
Petrosal sinus sampling of ACTH
What imaging may be useful in localising hypercorticolism?
MRI Sella
CT adrenals
CT chest
Bilateral inferior petrosal sinus sampling
