adrenal gland Flashcards
What are the 3 layers to the adrenal cortex? (from outside to in)
- zona glomerulosa
- zona fasiculata
- zona reticularis
What type of cells are found within the adrenal medulla?
chromaffin cells
Where are glucocorticoids, mineral corticoids and androgens released from?
- mineralcorticoids from zona glomerulosa
- glucocorticoids from zona faculata
- androgens and glucocorticoids from zona reticularis
State the main mineralcorticoids, glucocorticoids and androgens
- mineralcorticoids: aldosterone
- glucocorticoids: cortisol (also cortisone)
- androgens: DHEA, androstenedione- becomes testosterone and ostrogen
What type of hormones are glucocorticoids, mineralcorticoids, androgens, oestrogens and progestins?
steroids (derived from cholesterol)
How do steroids exert their effects?
theyre lipid soluable so enter cell, bind to nuclear receptors and modulate gene transcription
Describe how corticosteroids regulate gene transcription
- they diffuse across plasma membrane
- bind to receptors (which have chaperone proteins attached)
- binding dissociates chaperones
- receptor/ ligand complex moves into nucleus
- can dimerise with other receptors and bind to glucocoritcoid response elements
- or bind to transcription factors
- both regulate expression
How does aldosterone travel in blood?
mostly bound to albumin but some binds to transcortin (another carrier protein)
What does aldosterone do?
increases expression of Na/K pump in distal tubules and collecting ducts of nephron which leads to more reabsobtion of Na and so water and excretion of K+. More water in blood leads to higher blood pressure
What is the difference between primary and secondary hyperaldosteronism? Give some examples of each
primary: defect in adrenal cortex (bilateral idiopathic adrenal hyperplasia is most common, also conns syndrome)
secondary: due to overactivity of RAAS (renin producing tumour (rare), renal artery stenosis)
What is conns syndrome?
an aldosterone secreting adrenal adenoma
How can you distinguish between primary and secondary hyperaldosteronism?
primary: LOW RENIN
secondary: HIGH RENIN
What are signs of hyperaldosteronism?
high blood pressure (esp in young) LV hypertrophy Stroke Hypernaturaemia (High Na+) Hypokalaemia (Low K+) also headaches, fatigue
How is hyperaldosteronism treated?
depends on type:
- aldosterone producing adenomas removed surgically
- spironolactone is mineralcorticoid receptor antagonist
How is cortisol transported in the blood?
bound to transcortin
what effects does cortisol have on the body?
- increase protein breakdown
- incease gluconeogenesis in liver
- increase fat break down in arms and legs (redistributes to abdomen and dorso- cervical fat pad
- supresses immune and inflammatory response (inhibits macrophages and mast cell degranulation)
- resists stress (increases glucose supply, raise blood pressure by making vessels more sensitive to vasoconstriction)
- inihibits insulin induced GLUT4 translocation
What is the name for chronic excess cortisol
cushing’s syndrome
What can cause cushings syndrome?
- prescribed glucocorticoids
- benign pituitary adenoma secreting ATCH (cushings disease)
- excess cortisol from adrenal tumour (adrenal cushings)
- non- pituitary- adrenal tumours producing ATCH or rarely CRH eg small cell lung cancers
How can you differentiate between cushings disease, adrenal cushings and non pituitary- adrenal tumours producing ACTH?
- adrenal tumours producing cortisol (adrenal cushings) will lead to high cortisol levels but low ACTH
- Cushings disease will have high cortisol and ACTH but the ACTH will supress on a supression test (as it is from pituitary cells so has receptors to respond to neg feed back, but this response will be less than normal)
- non-pituitary- adrenal tumours producing ACTH will not react to supression test so ACTH and cortisol will always be high l
What are signs and symptoms of cushings disease?
- plethoric moon shaped face
- buffalo hump (fat on back of neck)
- abdominal obesity
- purple striae
- acute weight gain
- hyperglyaemia
- hypertension
- early stages sometimes present with easy bruising and bones breaking easily
When are steroid drugs such as prednisolone used?
- treatment of inflammatory disorders:
- asthma
- inflammatory bowel disease
- rheumatoid arthirits
- other auto immune conditions
- supress immune response after organ transplant
What are side effects of steroid drugs?
- hypertension
- weight gain
- insomnia (cortisol circadian rythm)
- headaches
- brusing
- achne
What is important about someone taking steroid drugs?
Their dose must be reduce slowly, the course cannot be stopped abruptly.
Why is it that those with cushings disease often have high Na+, low K+, hypertension and urea + creatinine mildly high?
- mildly high urea and creatine it due to more muscle proteolysis due to more cortisol
- high Na+ and low k+ is because cortisol has a similar structure to aldosterone so it will increase transcription of Na/k pump in the nephrons when its levels are very high
- leads to more Na in and more K excreted, as well as increasing BP
