Diagnosis of Adrenal Disorders Flashcards
What is the structure that is common to all steroids?
4 rings
What is cortisol also know as?
Hydrocortisone
What is cortisone?
Very weak glucocorticoid
Biologically inactive metabolite of cortisol
What happens to cortisone after administration to a patient?
Metabolised to cortisol in liver
What is the major glucocorticoid?
Cortisol
What is the action of glucocorticoids?
Stimulation of gluconeogenesis in liver
Mobilisation of amino acids in muscle
Stimulation of lipolysis in adipose tissues
Immunosuppression
What does too much cortisol lead to?
Weight gain Wasting of - Muscle - Skin - Bone Hyperglycaemia Salt retention > hypertension Inhibition of linear growth
What can cause ACTH-dependent hypercortisolism?
Pituitary adenoma = Cushing’s disease
Ectopic ACTH syndrome
What can cause ACTH-independent hypercortisolism = Cushing’s syndrome?
Adrenal adenoma/carcinoma
ACTH-independent nodular hyperplasia
Administration of glucocorticoids
What is the most common cause of Cushing’s syndrome?
Administration of glucocorticoids
What happens in abnormal states when you deliberately stimulate/suppress the hormone to test for its function?
Hormone won’t rise into normal range when you stimulate it
Won’t fall into normal range if you suppress it
What is a 24 hour urine assay useful for?
Tell you about variation throughout day
How do you investigate suspected Cushing’s syndrome?
24 hour urine free cortisol
Check diurnal variation: serum cortisol and plasma ACTH
at
- 8 am
- 12 am
Check negative feedback loop working: dexamethasone suppression test
Cranial MRI/adrenal CT as indicated
What is dexamethasone?
Very powerful glucocorticoid
What happens when someone is given dexamethasone?
Should decreased ACTH and cortisol
What does it mean if ACTH and cortisol don’t decrease when dexamethasone is given?
Something wrong with pituitary
What does not enough cortisol cause?
Can't cope with new stress; eg: infection - Much sicker than they should be GI symptoms - Anorexia - Nausea - Vomiting - Diarrhoea - Weight loss Salt wasting > low BP Darkening of skin if ACTH secretion stimulated Muscle weakness - Skeletal - Cardiac
What are the possible causes of adrenocortical insufficiency?
Genetic - Enzyme defect in cortisol biosynthesis - Metabolic defect = adrenoleukodystrophy Autoimmne adrenal destruction Infectious disease - Adrenal destruction by TB
What is the most common cause of Addison’s disease in Australia?
Autoimmune destruction of adrenal cortex
What are the clinical findings for Addison’s disease?
Salt-wasting state > low Na and high K
How do you treat Addison’s disease?
Cortisol
Fludrocortisone
Where does Addisonian pigmentation commonly occur?
Knuckles of hands
Knees
Gums and oral mucosa
General pigmentation
What happens when there is an excess of adrenal androgens?
Premature pubic hair Hirsutism Acne Enlargement of penis/clitoris in child Behavioural changes Linear growth spurt Rapid epiphyseal fusion in child Muscular habitus Deepening of voice
What is the cause of congenital adrenal hyperplasia (CAH) in 90% of cases?
21-hydroxylase deficiency
What is the inheritance pattern of CAH?
Autosomal recessive
What is the pathophysiology of CAH?
Variable impairment of cortisol and aldosterone synthesis > ACTH stimulation > adrenal hyperplasia > increased androgen > virilisation
What are the three different presentations of CAH in females?
Exposed to high levels of androgens in utero > infant with ambiguous genitalia
In utero androgens not that high > happens more slowly > premature pubic hair and enlarged clitoris
Adolescent hirsutism and acne
What are the presentations of CAH in males?
Adrenal crisis in baby aged 2-3 weeks
Premature sexual development at age 2-3 years
Why is there a decrease in oestrogen in CAH?
Made from testosterone and aromatase very tightly regulated
Do have slightly elevated levels
What is the most commonly used steroid treatment?
Prednisolone
What type of steroid is fludrocortisone?
Mineralocorticoid
What regulates aldosterone secretion?
Increase K in ECF
Angiotensin II
What are the actions of aldosterone?
Increased resorption of Na
Increased resorption of water
Increased excretion of K from kidney distal tubule
What does excess aldosterone (Conn’s syndrome) cause?
Salt retention > hypertension
Hypokalaemia > weakness
Low renin
What does a deficiency in aldosterone cause?
Dehydration
Salt depletion
Postural hypotension
Hyperkalaemia > cardiac arrhythmias
What are possible causes of Conn’s syndrome?
Adrenocortical tumour secreting aldosterone
What is the treatment for Conn’s syndrome?
Surgery
What does pheochromocytoma cause?
Secrete large amounts of adrenaline and noradrenaline from adrenal medulla
