ADRENAL STRUCTURE AND FUNCTION Flashcards
what is aldosterone under the control of?
renin
what are glucocorticoids under the control of?
ACTH
what are sex steroids under the control of?
ACTH
what are noradrenaline and adrenaline under the control of?
sympathetic nervous system
whats the most abundant hormone in the body?
dehydroepiandrosterone sulfate
whats secreted in higher amounts… gluco or mineralocorticoids
glucocorticoids
how do cortisol levels change throughout the day?
generally are higher in the morning when we wake up, and then fall throughout the day. This is called a diurnal rhythm (in people that do night shifts, this is reversed)
how does the body stop corticosteroids binding to mineralocorticoid receptors (because they are so similar instructor)>
11 beta HSD2 can deactivate active steroids to produce inert steroids
(at high concentrations, corticosteroids can escape this mechanism and exert its effects)
what is Addisons disease?
primary adrenal insufficiency
what is primary adrenal insufficiency?
◦ A rare endocrine disorder that happens when the adrenal gland cortex is damaged and so isnt able to produce enough hormones such as aldosterone and cortisol
what levels of cortisol, ACTH and CRH would you expect to see in primary adrenal insufficiency?
low cortisol, High ACTH and high CRH
whats Waterhouse-friderichsen syndrome?
sudden increase in bp causes blood vessels in the adrenal cortex to rupture, filling up the adrenal glands with blood and causing tissue ischaemia and adrenal gland failure.- can cause primary adrenal insufficiency
whats the most common cause of Addisons disease in HIC?
auto immune - where the cortex of the adrenal glands are attacked so cortisol and aldosterone cannot be produced.
what are some causes of Addisons disease in LICs?
infections (TB, fungal, cytomegalovirus), infiltration by metastases, infarction, haemorrhage, adrenoleukodystrophy
outline the significance of the adrenal cortex having a high functional reserve?
only a small amount of functional tissue can still do a pretty decent job of churning out enough hormones to meet the body’s needs. This means once there are symptoms, its usually a sign that the majority of the adrenal cortex has been destroyed.
what symptoms and signs does Addisons disease cause?
hyponatremia hyperkalaemia hypobolemia metabolic acidosis salty food cravings abdominal pain fever weight loss and anorexia nausea, vomit muscle and joint pain fatigue dizziness worse on standing disorientated hyperpigmentation loss of pubic and armpit hair in women decreased sex drive
why can Addisons disease cause hyperpigmentation?
This decreased cortisol level causes the pituitary gland to become overactive so we end up producing pro-opiomelanocortin which is a precursor to melanocyte-stimulating hormone
why doesnt the decrease in androgen production in Addisons disease cause issues for males?
because their primary site for producing androgens is the testes
what is an adrenal crisis?
when the majority of the zona glomerulosa and zona fasciculata are destroyed. It can cause sudden pain on lower back, abdomen or legs with severe vomiting and diarrhoe, followed by dehydration, low bp and loss of consciousness. If left untreated this can be fatal.
how can we diagnose Addisons disease?
random cortisol test
9am cortisol test
short synacthen test (diagnostic)
what is the short synacthen test?
synacthen which stimulates the adrenal gland as its chemically similar to ACTH, if the adrenal glands are working normally then blood samples taken shortly after should show a rise in cortisol.
what is secondary adrenal insufficiency?
lack of cortisol secretion due to lack fo ACTH release from pituitary gland
whats the msot common cause of secondary adrenal insufficiency?
HPA axis suppression from long term steroid use
how does secondary adrenal insufficiency present differently to Addisons disease?
no hyperpigmentation
no dehydation
no hyperalaemia
hypoglycaemia is more common
what is tertiary adrenal insufficiency?
Decreased level of CRH released from the hypothalamus. decreased levels of ACTH = decreased cortisol
what are some causes of tertiary adrenal insufficiency?
brain tumors, trauma to the base of the skull or sudden withdrawal from long-term use of exogenous steroids.
what are some causes of causes of secondary adrenal insufficiency?
pituitary tumour
glucocorticoid use
how is adrenal insufficiency treated?
3 x daily hydrocortisone
what can you give a patient whos deficient in aldosterone?
fludrocortisone
how should your dosing of steroids change when you have an illness or infection?
double the dose
what is a steroid card?
Recently issued national guidance promotes a new patient-held Steroid Emergency Card to help healthcare staff identify patients with adrenal insufficiency and provide information on emergency treatment if the patient is acutely ill, experiences trauma, surgery or other major stressors
what is cushings syndrome?
elevated levels of cortisol
whats the most common cause of cushings syndrome?
exogenous corticosteroid use which causes suppression of HPA axis which can last as long as a year depending on the dose of the steroid.
other causes include pituitary adenomas, ectopic sources of ACTh
what is cushings disease?
when ACTH producing pituitary adenoma causes hypercortisolaemia
what are some signs and symptoms of cushings syndrome?
- thinning and bruising of the skin
- buffalo hump
- moon face
- cardiac hypertrophy
- hyperkalaemia
- muscle wasting
- osteoporosis
- dark facial hair on women
- abdominal striae which are purple and thick
- amenorrhoea
- central obesity
- hypertension
- which messes up normal ovarian and testicular function
- dampens the inflammatory and immune response
- impairs normal brain function
why do patients with cushings syndrome get central obesity?
levated glucose -> elevates insulin -> actvates lipoprotein lipase so adipocytes can accumulate more fat molecules
why can cushings syndrome cause hypertension?
cortisol can start cross-reacting with mineralocorticoid receptores because its structurally similar and so can ahve mineralocorticoid efefcts and retain fluid.
why can cushings syndrome interfere with ovarian and testicular function?
• High levels of cortisol inhibit the secretion of gonadotropin releasing hormone from the hypothalamus
what can put a patient in a pseudo-cushings state?
alcoholism depression obesity anorexia bulimia
what are some tests for cushings syndrome?
24 hour urine free cortisol
1mg overnight dexamethasone suppression test
midnight serum cortisol
late night salivary cortisol
outline how the 1mg overnight dexamethasone suppression test works?
give dexamethasone at 11pm and then chetck cortisol at 9am - should drop in normal cases
