Clinical Aspects of the Adrenal Gland Clinical Case & Discussion Flashcards
What are the main hormones secreted by the adrenal gland?
- Aldosterone
- Cortisol
- DHEA and androgenic steroids
- Norepinephrine / epinephrine
What are the two most common diseases of adrenal hyposecretion?
- Addison’s disease
- Congenital adrenal hyperplasia (deficiency in one of the enzymes necessary for aldosterone / cortisol production, most commonly 21-hydroxylase)
Causes of Addison’s Disease? Pathophysiology?
- Autoimmune (90%)
- TB / metastasis
- Destruction of the adrenal cortices (via lymphocyte infiltration) results in steroid and mineralocorticoid deficiency
Symptoms of Addison’s disease?
- Weight loss / anorexia
- Weakness
- Malaise
- nausea
- Vomiting
- Diarrhoea
Clinical signs of Addison’s Disease?
- Skin pigmentation / vitiligo (loss of pigment in patches)
- Hypotension
- Hypoglycaemia
- Hyponatraemia
Investigations for Addison’s disease?
- Early morning blood [cortisol]: >450nmol/L not Addison’s
- Short Synacthen: administer tetracosactrin (ACTH) via IM / IV injection, if cortisol doesn’t rise significantly over 30-180min then likely Addison’s
How can you tell if low cortisol is due to primary adrenocortical insufficiency (Addison’s) or secondary insufficiency? (pituitary?)
- Check if plasma ACTH is suppressed or normal/elevated
Suppressed suggests secondary issue
Management of Addison’s disease? (or of low cortisol / aldosterone in general)
- Hydrocortisone: glucocorticoid replacement (cortisol)
- Fludrocortisone: mineralocorticoid replacement (aldosterone)
What should patients taking hydrocortisone do when they are ill? (infection / UTI)
- Double their hydrocortisone dose
What are some endocrine causes of hypertension?
- Phaeochromocytoma
- Acromegaly
- Cushing’s Syndrome
- Hyperparathyroidism
- Hypothyroidism / Hyperthyroidism
- Congenital adrenal hyperplasia
What are the adrenal disorders of hypersecretion?
- Cushing’s Syndrome (cortisol / sex steroids)
- Conn’s syndrome (aldosterone)
- Phaeochromocytoma (catecholamines)
Approximately what percentage of Cushing’s syndrome cases are ACTH independent? What are they mostly due to?
- 20% ACTH-independent
- Mostly due to adrenal tumour
Investigations for suspected Cushing’s syndrome?
- 24-h urine [free cortisol]
- Low dose dexamethasone test (measures responsiveness of adrenals to ACTH, cortisol should decrease after dexamethasone)
How does the dexamethasone test work? How can it differentiate between pituitary and adrenal causes of Cushing’s?
- Dexamethasone suppresses ACTH, gets administered overnight. Normally cortisol is suppressed the next morning due to this, if not abnormal cortisol secretion
- High dose of the drug will cause ACTH-dependent Cushing’s patients to have lower cortisol the next morning, ACTH-independent cortisol will not be affected by drug
What is the function of aldosterone and what does this mean for Conn’s syndrome patients?
- Aldosterone functions to increase water reabsorption at the kidney tubules
Conn’s patients:
- Increased blood volume
- Increased blood pressure
- Increased urine K (bc aldosterone causes Na reabsorption which water follows, but K moved into urine)
How does primary hyperaldosteronism differ from secondary hyperaldosteronism?
Primary: low renin activity in plasma, but still high aldosterone concentration and activity
Secondary: high renin activity in plasma causing the high aldosterone concentration and activity
Investigations for suspected Conn’s syndrome?
- Aldosterone : renin ratio (high in primary)
- Blood [Potassium] (low in Conn’s)
- 24 h urine aldosterone and Na (both high Conn’s)
- CT adrenal gland
Management of Conn’s syndrome?
- Spironolactone (aldosterone antagonist)
- Resection of adenoma / hyperplasia
What is phaeochromocytoma?
- Tumour of the adrenal medulla causing increased secretion of noradrenaline and adrenaline
- 90% benign unilateral
- 10% malignant / extra-adrenal / multiple
- 30% hereditary
Symptoms of phaeochromocytoma?
Paroxysmal:
- Headache
- Sweating
- Palpitations
- Tremor
- Pallor
- Hypertension
Investigations for phaeochromocytoma?
- 24h urinary catecholamines (from textbook)
- MRI adrenal
- PET adrenal
Management of phaeochromocytoma?
- phenoxybenzamine (alpha receptor blocker)
- Surgery to remove mass
Why does 21-Hydroxylase deficiency cause congenital adrenal hyperplasia?
- No 21-hydroxylase = no cortisol / aldosterone
- No negative feedback on ACTH production
- ACTH continuously stimulates adrenal gland, leads to hyperplasia
What are some symptoms of Addisonian Crisis (acute adrenal failure)?
Weakness, fatigue, anorexia, weight loss 100%
Skin pigmentation or vitiligo 92%
Hypotension 88%
Unexplained vomiting or diarrhoea 56%
