Adrenal gland Flashcards
What are the three layers of adrenal cortex/medulla and what hormones are they associated with respectively?
Zona glomerulosa - mineralocorticoids (aldosterone)
Zona fasciculata - glucocorticoids (cortisol)
Zona reticularis - adrenal androgens
Medulla - adrenaline/noradrenaline
What is the biosynthesis of steroids?
Cholesterol –> pregnenolone –> separate pathways
How are adrenal productions regulated?
Cortisol: hypothalamic-pituitary-adrenal axis
Aldosterone: renin-angiotensin system and potassium level
How is renin-angiotensin system activated?
when blood pressure drops
What are the major cortisol actions? and how can it be used therapeutically?
Principles of use:
Suppress inflammation
Suppress immune system
Replacement treatment
Role in treatment of:
- allergic disease
Inflammatory disease like RA, Crohn’s disease
Dark skin, dehydrated, hypotensive, hyponatremia, hyperkalaemia, young
Addison’s disease - primary adrenal insufficiency
You can see symptoms for both lack of mineralocorticoids and glucocorticoids
Other causes of primary adrenal insufficiency include: congenital adrenal hyperplasia, adrenal TB/malignancy
2nd/3rd adrenal insufficiency:
Due to lack of ACTH stimulation
Iatrogenic
Pituitary/hypothalamic problem
Clinical Addison’s Disease features
Anorexia, weight loss
Fatigue/lethargy
Dizziness and low BP
Abdominal pain, vomiting, diarrhoea
Skin pigmentation (due to conversion of ACTH to melanocyte stimulating hormone)
Addison’s
autoimmune destruction of adrenal cortex
- 90% can be destroyed before clinical symptoms
Diagnosis of adrenal insufficiency
hyponatremia, hyperkalaemia
(hypoglycaemia in kids)
Short synacthen test, measuring cortisol levels
ACTH levels, Renin/aldosterone
Adrenal autoantibodies (21-OH antibodies)
Mx adrenal insufficiency
Do not delay treatment to confirm diagnosis (unlikely to do harm)
Hydrocortisone as cortisol replacement
- give IV first if unwell, then shift to oral
- 15-30mg daily in divided doses
- try to mimic diurnal rhythm
Fludrocortisone as aldosterone replacment
- add only after patient can start drinking and eating well
- carefully monitor BP and K+
Need education for sick day rules (hydrocortisone), cannot stop suddenly (if continuously vomitting - take an IM hydrocortisone and arrange hospital admission), need to wear identification (emergency steroid card)
Adrenal crisis emergency
Saline
IV hydrocortisone
clinical features Secondary adrenal insufficiency (lack of CRH/ACTH)?
Similar to primary except:
Pale skin
Does not need aldosterone replacement
Clinical features of Cushing’s (too much cortisol)
commoner in women and ages 20-40
thinning of skin
Easy bruising
facial plethora
Striae
proximal myopathy
central obesity
Causes of endogenous Cushing’s syndrome
1st pituitary
2nd Adrenal
3rd ectopic ACTH
Too much aldosterone
hyperaldosteronism (Conn’s adenoma)
Endocrine causes of hypertension
High cortisol
high aldosterone
high GF (acromegaly)
high adrenaline
Primary aldosteronism
Autonomous production of aldosterone independent of its regulators (angiotensin II/potassium) - will result in low renin
Significant hypertension
Hypokalaemia in around 30%
Alkalosis
Diagnosis & Mx of PA
Step 1: confirm aldosterone excess
Establish plasma aldosterone to renin ratio
If such ratio is raised, perform saline suppression test
Failure of plasma aldosterone to suppress by 50% with 2 litres of normal saline confirms PA
Step 2: confrim subtype
- Adrenal CT to demonstrate adenoma
- Adrenal vein sampling to confirm adenoma is true source of aldosterone excess (as incidental adrenal lumps are rather common, and increase with age)
Only unilateral adenoma would consider surgery (cuz removal of both adrenal glands would cause permanent hypo-cortisol), and only surgical consideration would need imaging PET-CT
Bilateral adrenal hyperplasia - spironolactone as mineralocorticoid receptor antagonist
Congenital Adrenal Hyperplasia
Inherited disorder, deficiency in one of the enzymes necessary for cortisol synthesis
Usually identified in neonatal period
Diagnosis CAH
- Basal 17-OH Progesterone levels (lack of 21-hydroxylase would lead to everything converting into testosterone, 17-OH P is one of the precursors) –> this is the hormone most likely to be deficient in the pathway
- genetic test
Phaeochromocytoma (tumour of adrenal medulla or sympathetic chain, where it would be called paraganglioma)
Feels like panic attack - headache, sweats, palpitations
High levels of adrenaline/noradrenaline
MIBG scan (nuclear medicine scan) - check for disease elsewhere before surgery
Diagnosis for phaeochromocytoma/paraganglioma
- confirm excess of catecholamines, checking 24 urine or plasma metanephrine
Approach to therapy (PCMC)
Full alpha and beta blockade, only when sufficient alpha blockade [with phenoxybenzamine/doxazosin] (ie adequate BP control and evidence of postural drop), consider addition of b-blocker
B-blocker (propranolol, atenolol or metoprolol)
*Treatment: Surgery, total excision wherever possible, tumour de-bulking
Long-term follow-up, genetic testing, family tracing and investigation
