Adrenal Glands Flashcards
What are the three zones of the cortex and what do they secrete?
Zona glomerulosa - mineralocorticoids Zona fasciculata - glucocorticoids Zona reticularis - androgens
What does the medulla secrete?
Adrenaline
Describe ACTH
It’s hydrophilic and interacts with high affinity receptors in zona fasciculata and reticularis.
Describe what binding of ACTH causes
Binds to melanocortin receptor (corticotrophin) leading to activation of cholesterol esterase.
Describe the action of cortisol
Component of stress response. Increases proteolysis, lipolysis and gluconeogenesis.
Describe the action of aldosterone
Stimulates Na+ reabsorption in kidney in exchange for K+ (or H+)
Describe the action of androgens in males
Stimulate growth and development of male genital tract and secondary sexual characteristics including height, body shape, facial and body hair, lower voice pitch. Also have anabolic actions on muscle proteins
What happens if there is over-secretion of androgens in females?
Hirsuitism, acne, menstrual problems, virilisation, increased muscle bulk, deepening voice
Describe the effects of oestrogens in females
Stimulate growth and development of female genital tract, breasts and female secondary characteristics including broad hips, accumulation of fat in breasts and buttocks, body hair distribution. Weakly anabolic and decrease circulating cholesterol levels
How does adrenaline affect its target cells?
Binds to adrenoreceptors on the outside of the cell activating a secondary messenger
How is cortisol secretion controlled by ACTH and CRH?
How is adrenaline synthesised?
Tyrosine - dopa - dopamine - noradrenaline - adrenaline
List a few of the actions of adrenaline
CVS - increases cardiac output and bloody supply to muscle, CNS - mental alertness, carbohydrate metabolism - glygogenolysis, lipid metabolism - lipolysis
What are the clinical implications of over-secretion of adrenaline?
Hypertension, palpitations, sweating, anxiety, pallor and glucose intolerance
What is the usual reason for over-secretion of adrenaline?
A tumour (phaemochromocytoma)
Explain the mechanism of action of cortisol
Crosses plasma membranes and binds to cytoplasmic receptors. Hormone/receptor complex then changes the rate of transcritption
What happens when there is an excess of glucocorticoids secreted?
Cushing’s Syndrome
What are the possible causes of Cushing’s Syndrome?
Increased activity of adrenal cortex due to tumour (adenoma), ectopic secretion of ACTH
List a few possible signs and symptoms of excess cortisol?
Increased muscle proteolysis and hepatic gluconeogenesis (steroid diabetes), muscle wasting, increased lipogenesis, catabolic effects on proteins etc
Give some symptoms of Cushing’s Syndrome
Moon-shape face, weight gain, immunosuppressive response - increased acne and bacterial infections, purple striae
What are the possible causes for Addison’s Disease?
Diseases of adrenal cortex reducing glucocorticoids and mineralocorticoids, decreased secretion of ACTH or CRH
Describe Addison’s Disease
Insidious onset, increased pigmentation, points of friction, buccal mucosa, decreased blood pressure, postural hypotension
What is an Addisonian Crisis
Nausea, vomiting, exterme dehydration, hypotension, confusion, fever and even coma
Describe the high dose dexamethasone suppression test
If the tumour is in the pituitary gland then ACTH and cortisol will decrease, if it’s ectopic then ACTH and cortisol will remain elevated despite the dexamethasone
Describe the syncathen test
Normally increases plasma cortisol - normal response usually excludes Addison’s Disease
Distinguish between Cushing’s Disease and Cushing’s Syndrome
Cushings Disease - Increased secretion of ACTH from pituitary
Cushing’s Syndrome - Hypercortisolism
How is it possible for cortisol to bind to mineralocorticoid and angroden receptors?
They have three main regions (hydrophobic hormone binding region, DNA-binding region and a variable region) - sequence homology
