Adrenal Glands Flashcards
What are the hormones produced by the cortex of the adrenal glands?
Mineralocorticoids e.g. aldosterone - zona glomerulosa
Glucocorticoids e.g. cortisol - zona fasiculata
Glucocorticoids and small amounts of androgens - zona reticularis
Describe steroid hormones.
All synthesised from cholesterol in adrenal glands and gonads
Lipid soluble
Bind to receptors of nuclear receptor family to modulate gene transcription
Describe the action of corticosteroids
Readily diffuse across plasma membrane
Bind to glucocorticoid receptors
Binding causes dissociation of chaperone proteins
Receptor ligand complex translocates to nucleus
Dimerisation with other receptors can occur
Receptors bind to glucocorticoid response elements or other transcription factors
What are the carrier proteins of aldosterone?
Mainly serum albumin and transcortin (to a lesser extent)
What is the RAAS?
Renin-angiotensin-aldosterone-system.
Acts to increase blood pressure and volume upon hypotension and/or hypovolaemia
Describe causes of secondary hyperaldosteronism
Signs: high BP, left ventricular hypertrophy, stroke, hypernatraemia, hypokalaemia
Treatment: depends on type, aldosterone-producing adenomas removed by surgery, spironolactone (mineralocorticoid receptor antagonist)
Where is cortisol produced? What tropic hormone regulates secretion of cortisol?
Produced and released by zona fasiculata in response to ACTH (from anterior pituitary)
What are the effects of cortisol?
Increased proteolysis in muscle
Increased lipolysis in fat
Increased gluconeogenesis in liver
Resistance to stress (increased supply of glucose, raised blood pressure by making vessels more sensitive to vasoconstrictors)
Anti-inflammatory effects (inhibits macrophage activity + mast cell degranulation)
Depression of immune response (prescribed to organ transplant patients)
Describe the hypothalamic-pituitary-adrenal (HPA) axis
Stress stimulates hypothalamus to release CRH -> stimulates anterior pituitary to release ACTH -> stimulates adrenal cortex to produce and secrete cortisol (-> negative feedback to hypothalamus and anterior pituitary)
What are the net effects of glucocorticoid action on metabolism?
Increased glucose production
Proteolysis
Redistribution of fat
What are steroid drugs (e.g. prednisolone and dexamethasone) used to treat?
Inflammatory disorders e.g. asthma, inflammatory bowel disease, rheumatoid arthritis, other auto-immune conditions
Also used to suppress immune reaction to organ transplantation
Side-effects are the same as the effects of higher levels of cortisol, plus can also have mineralocorticoid effects
How should steroid medication be halted?
Should be reduced gradually, not stopped suddenly - can lead to addisonian crisis if stopped suddenly
What are the sign and symptoms of Cushing’s syndrome?
Plethoric moon-shaped face
Buffalo hump
Abdominal obesity
Purple striae
Acute weight gain
Hyperglycaemia
Hypertension
What are the causes of Cushing’s syndrome?
EXTERNAL CAUSES: prescribed glucocorticoids
ENDOGENOUS CAUSES: benign pituitary adenoma secreting ACTH (Cushing’s disease); excess cortisol produced by adrenal tumour (adrenal cushings); non pituitary-adrenal tumours producing ACTH (&/or CRH) e.g. small cell lung cancer
