Hypoadrenalism tutorial Flashcards
Tests for suspecting addison’s
Look at ACTH at 9am (should be low due to high cortisol) and cortisol, synacthen (give ACTH and should get surge of cortisol),
K+ and Na+, can also look for autoantibodies
How does aldosterone work in DCT
Diffuses into cell, binds to MIneralocortioc receptor, upregulates Na+/K+ On basolateral membrane and Na+ channel in apical membrane
What is destroyed in Addison’s
Whole cortex- you need to lose 80% of the cortex to have symptoms
Why is POMC increased
Because the negative feedback is lost due to very low cortisol
Treatment
Immediately- saline to increase BP
Later- cortisol replacement (with hydrocortisone- give high in morning and low at night)
Why is cortisol high in the morning
It liberates glucose for energy for the day
How does cortisol increase blood glucose
Increases glycogenolysis enzymes and can also increase fat and protein breakdown
Tests for Cushing?
Urine 24hr cortisol Blood cortisol (in the evening because in the morning it is high anyway) Dexamethasne suppression test (giving synthetic steroid strong version of cortisol which should switch off ACTH but doesn't in cushings)'
Dex test would show what in adrena tumour vs pituitary
Pituitary- high ACTH even after dex, and high cortisol
Adrenal adenoma- low ACTH after dex and high cortisol
Why do you get centripetal obesity
Constantly high levels of blood sugar due t Cortisol breaking down all sugar from liver and other cells
Effect of cortisol on insulin
Normally suppresses it. But in Cushings, central adipocytes remain sensitive to insulin so keep storing sugars etc but
Why does BP increase with excess cortisol
Normally 11B-HSD metabolises cortisol to aldosterone but if cortisol increases so much it will overwhelm this enzyme and basically act as aldosterone in the kidneys increasing sodium and water retention
Why is placenta have high 11B-HSD
Cortisol is growth suppressant because it’s a stress hormone and growth is not necessary in stress,you need sugar elsewhere. In pregnancy if mum is stressed cortisol can be high and overwhelm this enzyme in placenta too
Cause for proximal myopathy
Cortisol will increase the metabolism of,protein to make glucose
What drug could be given before and after surgery
Metyrapone
