adrenal pathway dysfunction Flashcards
What biochemical molecule are steroid hormones made from?
cholesterol
which steroid hormones are produced in the adrenal cortex?
- mineralocorticoids (aldosterone)
- Glucocorticoids (cortisol)
- Sex steroids (androgens, oestrogens)
Angiotensin 2 activates which enzymes and produces which hormone?
- side chain cleavage
- 3 hydroxysteroid dehydrogenase
- 21 hydroxylase
- 11 hydroxylase
- 18 hydroxylase
aldosterone
ACTH activates which enzymes in the adrenal, producing which hormone?
cortisol
- side-chain cleavage
- 3 hydroxysteroid dehydrogenase
- 17 hydroxylase
- 21 hydroxylase
- 11 hydroxylase
what does aldosterone do?
stimulates sodium reabsorption in distal convoluted tubule and collecting duct, stimulates potassium and H+ secretion into urine
causes water to follow sodium back into blood by osmosis, increasing blood volume
therefore
increases blood pressure, sodium and lowers potassium
Addison’s disease is what kind of adrenal failure?
primary adrenal failure
what is the most common cause of addison’s disease in the UK?
Autoimmune destroying adrenals
What is the most common cause of Addison’s disease worldwide?
tuberculosis of adrenal glands
These are a symptom of what disease:
- hyperpigmentation
- low BP
- weakness
- weight loss
- nausea and GI problems
- vitiligo
Addison’s disease (primary adrenal failure)
Why is there increased pigmentation in Addison’s disease?
Lack of negative feedback of cortisol to the anterior pituitary, driving ACTH upwards.
pro-opio melanocortin is the precursor of ACTH and is broken down to ACTH and MSH (melanocyte-stimulating hormone)
Therefore increased production of ACTH also results in equally increased production of MSH
Why do people with addison’s disease have low blood pressure?
no cortisol or aldosterone
what are the consequences of adrenocortical failure?
- fall in BP
- loss of salt in urine
- increased plasma potassium
- fall in glucose due to glucocorticoid deficiency
- eventual death due to hypotension if untreated
What is the test for Addison’s?
- 9am cortisol
- Gie 250micrograms synacthen (synthetic ACTH) and measure cortisol response - will be low-zero
What will be the levels of ACTH and cortisol in the 9am cortisol test in Addison’s?
low cortisol
high ACTH
why do we give fludrocortisone instead of aldosterone when treating Addison’s disease?
fludrocortisone has a long enough half-life to be given once daily
what are the drugs that can be given for Addison’s disease and why?
- Fludrocortisone to replace aldosterone
- Prednisolone once daily or hydrocortisone 3x daily
What does of fludrocortisone should be given once daily?
50-100mg
Which drug: prednisolone or hydrocortisone, has a suitable half-life to mimic cortisol?
prednisolone
What dose should hydrocortisone be given at, and why?
3x daily 10 + 5 + 2.5mg to mimic diurnal rhythm
What does of prednisolone should be given?
3mg daily
What is the downside of using hydrocortisone 3x daily?
produces peaks which are unnatural and can affect metabolism and sleep
Congenital 21 hydroxylase deficiency causes an increase in which hormones?
sex steroids
why do people with congenital 21 hydroxylase deficiency have adrenal hyperplasia?
large amount of ACTH produced to try and stimulate hormone release
