Adrenal Glands Flashcards
What are the layers of the adrenal glands from superficial to deep?
Capsule
Cortex
Medulla
What are the layers of the adrenal cortex from superficial to deep?
Zona glomerulosa
Zona fasicualta
Zona reticularis
What type of hormone is secreted from the adrenal cortex, and how do they act?
Corticosteroids, lipid soluble
Bind to nuclear receptors and modulate gene transcription
How do corticosteroids regulate gene transcription?
1) readily diffuse across cell membrane
2) bind to glucocorticoid receptors
3) binding causes dissociation of chaperone proteins
4) receptor ligand complex translocates to nucleus
5) dimerisation with other receptors
6) receptors bind to glucocorticoid response elements or other transcription factors
What type of hormone is secreted by the zona glomerulosa?
Mineralocorticoids eg aldosterone
What are the effects of aldosterone?
Central component of RAAS, increases blood pressure and volume
Mainly acts on DCT and CT on nephron
Promotes expression of Na/K ATPase => increase reabsorption of Na and excretion of K
What is hyperaldosteronism?
Increased levels of aldosterone
What causes primary hyperaldosteronism?
Defect in the adrenal cortex
Aldosterone secreting adenoma => Conn’s syndrome
Bilateral idiopathic adrenal hyperplasia
Low renin levels
What causes secondary hyperaldosteronism?
Overactivity of RAAS
Renin producing tumour
Renal stenosis
High renin levels
What are some signs of hyperaldosteronism?
High BP
Left ventricular hypertrophy
Stroke
Hypernatraemia and hypokalaemia
What is the treatment for hyperaldosteronism?
Remove aldosterone secreting adenomas
Spironolactone - aldosterone receptor antagonist
What does the zona fasiculata secrete?
Glucocorticoids
What causes Cushing’s syndrome?
Excess cortisol
Exogenous: prescribed steroids
Endogenous: Cushing’s disease (pituitary adenoma), excess cortisol from adrenals, ectopic ACTH secretion from small cell lung carcinoma
What causes Addison’s disease?
Chronic adrenal insufficiency
Possibly an autoimmune response
What are some signs and symptoms of Addison’s disease?
Postural hypotension Increased skin pigmentation Hypoglycaemia Weight loss and anorexia Lethargy
What causes hyperpigmentation in Addison’s?
Decreased cortisol => increased POMC (required to synthesise ACTH) => MSH
POMC is split into ACTH and MSH
What is an Addisonian crisis?
Life threatening emergency due to adrenal insufficiency
Precipitated by;
Severe stress, salt depravation, infection & abrupt withdrawal of steroids
What are some symptoms of an Addisonian crisis?
Nausea Vomiting Pyrexia Hypotension Vascular collapse
What is the treatment for an Addisonian crisis?
IV hydrocortisone
IV 0.9% saline, 500ml bolus
U&Es - check for hyperkalaemia
What are the effects of glucocorticoids?
Increase glucose production
Breakdown of protein
Redistribution of fat
What hormones are secreted by the zona reticularis?
Androgens - DHEA and androstenedione
What is the action of androgens in males?
Converted to testosterone in the testes
What is the action of androgens in females?
Converted to oestrogen by other tissues
Only source of oestrogen post-menopause
What type of hormone is secreted from the adrenal medulla?
Catecholamines - adrenaline and noradrenalin
What is a phaeochromocytoma?
Catecholamine secreting tumour of the adrenal medulla
What are some symptoms of a phaeochromocytoma?
Anxiety Palpitations Tremor Sweating Weight loss
What biochemical changes are seen in Addison’s disease?
Hyponatraemia, hyperkalaemia
Raised urea
Hypoglycaemia
Mild anaemia
What test is done to confirm Addison’s disease?
Low 9am cortisol with a raised ACTH
Synacthen test confirms
What is the treatment for Addison’s disease?
Replace steroids
Hydrocortisone
Mineralocorticoids to correct postural hypotension & electrolyte imbalances
What should patients with adrenal insufficiency carry/have at home?
Carry steroid emergency card, wear medical alert bracelet
Don’t abruptly stop steroids
Should have some IM hydrocortisone
What investigations are done for a phaeochromocytoma?
24hr urinary metanephrine
Localise with abdominal CT
What are some signs of a phaeochromocytoma?
Malignant HTN - suspect if not responding to treatment
Tachycardia
Orthostatic hypotension
What is the treatment for a phaeochromocytoma?
Surgery to remove
Requires α blocker before - phenoxybenzamine
Genetic screening
