The Adrenal Gland Lecture Flashcards
Anatomy of adrenal gland
- 4-5g
- 90% is cortex surrounding medulla
- Arterial supply from renal arteries, aorta and inferior phrenic artery
- Venous drainaing right –> IVC, left –> left renal vein
Venous drainage important to note for sampling
3 zones of cortex
- Zona glomerulosa
- Zona fasiculata
- Zona reticularis
GFR
What does each zone produce?
- G - mineralocorticoids (salt) Aldosterone under RAAS control
- F - glucocorticoids (sugar) cortisol under ACTH control
- R - androgens (sex) DHEA and andronstenedione under ACTH control
Significance of aldosterone not being under ACTH control
If have pituitary problem, aldosterone will not need to be replaced as won’t be affected
Normal amount of aldosterone and cortisol and DHEA daily
- Aldosterone 100-150mcg/day
- Cortisol - 10-20mg/day
- DHEA - 10mg/day
Causes of mineralocorticoid deficiency
- Congenital eg congenital adrenal hyperplasia 21-hydroxylase deficiency
Acquired:
* primary adrenal insuffiency,
* secondary due to low renin in renal tubular acidosis (diabetes)
* Drug induced eg heparin, ciclosporin
Treatment for mineralocorticoid deficiency
Fludrocortisone 50-100mcg / day
Cautions with fludrocortisone
- Can cause fluid overload - HF caution
- Can cause hypokalaemia
Adrenal insufficiency causes
- Addisons
- Congenital adrenal hyperplasia
- Secondary - hypothalamic or pituitary dysfunction
Causes of primary adrenal insufficiency - acquired
- Autoimmune
- Malignancy (mets or lymphoma)
- Infiltration - sarcoidosis, amyloidosis
- Infection - TB, fungal, HIV
- Vascular - haemorrhage, meningococcal septicaemia
- Infarction - thrombosis
Causes of congenital primary AI
- CAH
- CLAH
- Triple A syndrome
- X linked adrenal leukodystrophy
Causes of primary AI iatrogenic
- Bilateral adrenalectomy
- Drugs - etomidate, ketoconazole, mitotane
Causes of secondary AI - more common than primary
- Tumours
- Infection
- Infiltation
- Isolated ACTH deficiency
- Exogenous steroid use suppressing axis
Clinical features of AI - primary
- Anorexia
- Weight loss
- Tiredness
- Weakness
- Hyperpigmentation
- Dizziness and postural hypotension
- N+V
- Abdo pain
- Arthralgia
- Myalgia
- Reduced libido and pubic hair
- Salt craving
Secondary AI clinical features
- Same as primary
- BUT no hyperpigmentation as there is no increased ACTH to cause this - no mineralocorticoid deficiency
- Low ACTH is the problem in secondary remember
Investigation for AI - findings
- Hyponatraemia
- Hyperkalaemia
- Elevated urea
- Anaemia
- Eosinophilia
- Hypercalcaemia (mild)
- Hypoglycaemia
Investigations for AI
- 9am cortisol (should be peak)
- ACTH
- TFTs
- Short synacthen test
- Renin - increased in primary
- Adrenal antibodies
- CT scan +/- biopsy?
What is SST?
- 9am cortisol bloods
- Administer ACTH
- Do bloods 30mins and 60 mins after
- Cortisol should double
Treatment for AI
- Glucocorticoid - hydrocortisone BD/TDS
- Mineralocorticoid - Fludrocortisone
- DHEA replacement? - not usually needed
Advice for someone on replacement for AI
- Sick day rules - double steroid dose
- Steroid card
- Emergency pack -has IM hydrocortisone if adrenal crisis, go to hospital if inject
Management of adrenal crisis
- O2
- IV access
- Fluids 0.9% NaCl
- Dextrose in cases of hypoglycaemia
- Hydrocortisone IV 100mg bolus then every 6hrs for 24-48hrs (then titrated down)
- Fludrocortisone when HC dose less than 50mg
Be mindful of chronic hypoNa - no more than 10-15mmol/L in 24hrs
Presentation of adrenal crisis
- Hyponatraemia
- Hyperkalaemia
- Hypoglycaemia
- Shock
When to investigate for secondary causes of HTN?
- If less than 40
- Resistant to medication
- Hypokalaemia
Causes of mineralocorticoid excess
- Primary aldosteronism (Conns - adenoma, bilateral hyperplasia, GRA)
-
- Secondary - RTA, renovascular, cirrhosis, CHF, nephrotic syndrome, renin secreting tumour (all increases renin)
Other:
* Liqourice
* Ectopic ACTH
* Exogenous
Most common cause primary hyperaldosteronism
Bilateral hyperplasia
What is GRA?
Glucocorticoid-remediable Aldosteronism
When ACTH activates aldosterone instead of RAAS
Presentation of hyperaldosteronism
- Under 40
- Resistant hypertension
- Hypokalaemia
Investigations for hyperaldosteronism
- Aldosterone renin ratio
- Saline infusion - usually suppresses
- Fludrocortisone suppression
- Captopril supression
- Genetic testing if GRA
- Localise - CT/MRI, adrenal venous sampling, radiolabelled sampling
Things that can effect aldosterone renin ratio
- Beta blockers can cause false +ve
- ACEi can cause false -ve
- Spironolactone needs to be stopped 4-6 weeks prior test
Treatment primary hyperaldosteronism
- Surgery - laparascopic adrenalectomy
- Medical - mineralocorticoid receptor antagonists eg spironolactone, eplerenone
GRA management
- Low dose dexamethasone - suppress the ACTH
Causes of Cushings syndrome ACTH independent
- Adrenal adenoma
- Adrenal carcinoma
- Bilateral micro/macronodular hyperplasia
Associated features of Cushings syndrome - systemic
- HTN
- DM
- Osteoporosis
- Recurrent infections
Investigations for Cushings syndrome
- 24hr urine free cortisol - x2
- Overnight dexamethasone suppression test
- Salivary cortisol
- Midnight cortisol
- Low dose DMT or HDDT
- ACTH, serum K, CRH
- CT adrenal if points to this
Step1 - find raised cortisol, step 2 check ACTH, step 3 adrenals
Treatment for Cushings syndrome adrenal
- Adenoma - unilateral adrenalectomy
- Carcinoma - surgery, chemo, adrenolytic agents
- Bilateral hyperplasia - bilateral adrenalectomy
What is phaechromocytoma?
- Tumour arising from adrenal medulla
- 10% bilateral, 10% FH, 10% malignant
When to screen for phaechromocytoma?
- Young pts with HTN
- Adrenal incidentaloma
- Unexplained HF
- Hypertensive crisis during general anaesthesia
Gene mutations associated with phaechromocytoma
- Multiple endocrine neoplasia (MEN)
- VHL - Von Hippel Lindau
- NF - neurofibromatosis
- SDH - tumour supressor mutation
- MAX
- TMEM
Investigation for phaechromocytoma
- 24hr urine catacholamines/metanephrines
- Plasma metanephrines (more sensitive, less specific)
- Localise - CT, MRI, MIBG, FDG PET
Management of phaechromocytoma
- Alpha blockade (FIRST) eg Phenoxybenzamine
- Beta blockage
- Monitor BP, haematocrit and fluid status
- Surgical resection when stable
Management of phaechromocytoma crisis
- ICU admission
- Ventilation may be needed due to extreme hypoxia
- Alpha blockade with phenoxybenzamine and prazosin
- Correct IV volume - IV fluids and high salt
- Beta blockade after adequate alpha
- Surgical removal
Why alpha blockade before beta?
Avoid unapposed alpha adrenergic activity
