Adrenal Cortex Flashcards
What do the layers of the adrenal cortex secrete?
Zona glomerulosa: mineralocorticoids e.g. aldosterone
Zona fasciculata: glucocorticoids e.g. cortisol
Zona reticularis: androgens e.g. testosterone + glucocorticoids
What does the adrenal medulla secrete?
Noradrenaline & adrenaline (catecholamines)
What types of hormones does the adrenal gland secrete? What is the precursor?
Steroid hormones, therefore cholesterol is the precursor
What do glucocorticoids do?
- stimulate gluconeogenesis & glycogenesis, protein catabolism, lipolysis at low levels but lipogenesis at higher levels
- minor effect similar to mineralocorticoids
What do mineralocorticoids do?
- Na+ retention
- K+ loss
What do androgens do?
- testes formation
- spermatogenesis
- increase in muscle mass
- decrease in fat deposition
- estradiol production
What does a deficiency/excess in mineralocorticoids cause?
Deficiency: decrease in Na+, increase in K+ —> dehydration due to osmotic diuresis
Excess: increase in Na+, decrease in K+ —> hypertension (high [salt] circulating)
What does a deficiency/excess in androgens do?
Deficiency:
- osteoporosis
- erectile dysfunction
- gynaecomastia
Excess:
- clitoromegaly (females)
- hypotension
What does a deficiency in cortisol cause? What are the signs and symptoms?
Addison’s disease
Non-specific S&S:
- weight loss
- weakness
- fever
- depression
- impotence
- amenorrhoea
- low libido
- abdominal pain
- myalgia
- nausea
Specific S&S:
- hyperpigmentation (ACTH build up - minor effect similar to alpha-MSH, stimulates melanin production)
- postural hypotension (BP drops when standing up)
What are the biochemical features in Addison’s disease?
Natraemia (low Na+)
Hyperkalaemia (high K+)
High urea
Hypoglycaemia
How can Addison’s disease be diagnosed?
Test [cortisol] (morning)
Syacthen test (synthetic ACTH —> won’t stimulate production)
[ACTH]blood (high)
[renin]plasma (low - mineralocorticoids cause an increase in renin)
adrenal antibodies (presence of)
What is the mechanism of Addison’s disease?
Autoimmune destruction of adrenal cortex
(or: TB, surgical removal of adrenal cortex, haemorrhage/infarction/infiltration of adrenal cortex, or adrenal leucodystrophy)
What is the treatment for Addison’s disease?
Glucocorticoid & mineralocorticoid replacement (using hydrocortisone & fludrocortisone) Monitor cortisol levels daily Restore to normal weight Supress plasma renin Restore serum electrolytes to normal
What is an Addisonian crisis? What is the emergency treatment? How can it be distinguished from a diabetic coma?
Deficiency of corticoids leading to osmotic diuresis —> low circulating volume —> low perfusion to brain —> DEATH
Hydrocortisone + fludrocortisone, replace fluids, dextrose (for hypoglycaemia)
Hypotension (diabetic coma = hypertension)
What are the general signs and symptoms of Cushing’s syndrome?
- central adiposity
- weight gain
- depression
- insomnia
- low libido
- thin skin (easily bruised)
- hair growth
- acne
- muscle weakness & wasting (thin arms and legs)
- impaired glucose tolerance
- plethoric (flushed) moon face
- buffalo hump (dorsal fat pad)
- purple striae (stretch marks)
What are some of the causes of Cushing’s syndrome?
- pituitary tumour (benign adenoma)
- adrenal tumour/hyperplasia
- ectopic ACTH-secreting tumour
- cortisol-secreting tumour
- steroid treatment
How can the cause of Cushing’s syndrome be diagnosed?
- [CRH] (high in pituitary tumour)
- [ACTH]plasma (high in pituitary/ectopic tumour)
- 24hr urinary excretion of cortisol (high in adrenal/ectopic tumour)
- dexamethasone suppression test
(low dose: no response to suppression of ACTH confirms Cushing’s syndrome; high dose: response = pituitary tumours = Cushing’s disease, no response = ectopic/adrenal tumour)
What is the treatment for Cushing’s syndrome?
Trans-sphenoidal surgery to remove pituitary tumours
Pituitary irradiation (pituitary tumours)
Bilateral adrenalectomy (adrenal tumours) (note: can cause Nelson's syndrome = uncontrolled pituitary growth and hyperpitutarism)
What is the difference between primary and secondary gland failure?
Primary gland failure:
Failure of end organ gland -> reduced end hormone -> increased pituitary hormone (overcompensation)
e.g. primary hypothyroidism
Secondary gland failure:
Failure of pituitary gland -> reduced end hormone -> reduced pituitary hormone
e.g. secondary hypothyroidism
