Endo - Adrenal Disorders Flashcards
(31 cards)
What is a steroid?
a chemical that comes from cholesterol
What enzymes are needed for the synthesis of aldosterone?
angiotensin II activates: → side chain cleavage → 3 hydroxysteroid dehydrogenase → 21 hydroxylase → 11 hydroxylase → 18 hydroxylase
What enzymes are needed for the synthesis of cortisol?
ACTH activates: → side chain cleavage → 3 hydroxysteroid dehydrogenase → 17 hydroxylase → 21 hydroxylase → 11 hydroxylase
What are the actions of aldosterone?
→ controls BP
→ controls sodium
→ lowers potassium
When is the best time to measure cortisol?
early in the morning
What is Addison’s disease?
primary adrenal failure
→ adrenal glands don’t produce sufficient hormones
→ pituitary produces too much ACTH + MSH
What is the world’s no.1 common cause of Addison’s?
tuberculosis of adrenal glands
What are the symptoms of Addison’s disease?
→ hyperpigmentation → hypotension → weakness → weight loss → vitiligo → gastrointestinal issues (nausea, diarrhoea, vomiting, constipation, ab pain)
Why do Addison’s disease patients have hyperpigmentation?
→ POMC is precursor for ACTH
→ when cleaved to produce ACTH, MSH is also produced
What are the 2 main mechanisms that cause adrenal failure generally?
→ enzymes in steroid synthetic pathway not working
→ adrenal glands destroyed
What is the most common cause of Addison’s Disease in the UK?
autoimmune Addison’s disease
What are 3 causes of adrenocortical failure?
→ TB Addison’s disease
→ autoimmune Addison’s disease
→ congenital adrenal hyperplasia
What are clinical consequences of adrenocortical failure?
→ fall in BP
→ loss of salt (sodium) in urine
→ increased plasma potassium
→ fall in glucose due to glucocorticoid deficiency
How can you test for Addison’s?
→ 9 am cortisol = low
→ ACTH = high
→ short synACTHen test (give 250 ug synacthen IM + measure cortical response)
Why can’t you treat Addison’s with pure aldosterone?
→ half life of aldosterone too short for safe once daily administration
→ has to be done through IV
What can you treat Addison’s disease with for aldosterone replacement?
fludrocortisone
→ aldosterone + fluorine
→ does not exist naturally
→ non-biodegradable
Why can’t you treat Addison’s with pure cortisol?
→ too short of a high life
→ too short for daily administration - has to be given thrice but causes late peaks of cortisol
→ late peaks in cortisol are harmful
Why can you treat Addison’s with for cortisol replacement?
hydrocortisone → longer half life → more potent than cortisol → 2.3 x binding affinity prednisolone → longer half life (more accurate for cortisol diurnal rhythm) → more potent than cortisol → 2.3 x binding affinity
What is a major cause of congenital adrenal hyperplasia?
21-hydroxylase deficiency
→ can be complete or partial
What hormones are deficient in congenital adrenal hyperplasia?
aldosterone + cortisol
How long can a baby survive with complete 21 hydroxylase deficiency?
less than 24 hrs
Which hormones are in excess in 21 hydroxylase deficiency?
sex steroid + testosterone
How will the baby present with 21 hydroxylase deficiency?
→ salt-losing Addisonian crisis (the placenta would’ve been feeding it nutrients)
→ girls may have ambiguous genitalia (excess of sex steroids causes virilisation of genitlia)
At what age do patients with partial 21 hydroxylase deficiency present?
any age after survival
