the hypothalamic pituitary adrenal axis Flashcards
what types of hormone does the adrenal cortex secrete?
glucocorticoid such as cortisol. mineralocorticoid- aldosterone. sex steroids- androgens.
what is the role of 11-b-hsd-2 and 1?
11-b-hsd-2 converts cortisol into corisone which is inactive. this allows aldosterone to bind to the mineralcorticoid receptor instead of cortisol, increasing specificity for the receptor. 11-b-hsd-1 converts cortisone into cortisol.
what disease is associated with too much cortisol and what are the symptoms?
Cushing syndrome. weight gain, central obesity (puffy face), buffalo hump, hypertension, insulin resistance, neuropsychiatric problems, osteoporosis.
what are the causes of cushings syndrome?
pituitary adenoma, adrenal tumour, ectopic ACTH. ACTH stimulates the release of cortisol.
what does latrogenic mean?
caused by steroid treatment.
What disease is associated with too little levels of cortisol and what are the symptoms?
Addisons disease. Darkening areas of skin (hyperpigmentation) Severe fatigue. Unintentional weight loss. Gastrointestinal problems, such as nausea, vomiting and abdominal pain. Lightheadedness or fainting. Salt cravings. Muscle or joint pains.
What causes addisons disease?
autoimmunity or rarely, metastases or TB.
what are the clinical signs of addisons disease?
low levels of all adrenocortical hormones.
How do you test the function of the HPAA?
blood- cortisol, ACTH- take into consideration the circadian rhythm (peak at 9am) and stress about the blood test or general stress.
urine- cortisol
saliva- cortisol- can do it late at night at home with no stress and late at night so no peak.
Stimulated- sinacthin- synthetic ACTH, can inject a person with this and see how their adrenals respond.
Can give someone insulin and make them hypoglycaemic and see how their adrenals respond.
supression- dexamethason is a glucocorticoid, which would stop pituitary, would stop the whole axis because thats what cortisol does it works as a negative feedback loop.
How do you test for someone making too much cortisol?
24 hour urinary test.
midnight cortisol saliva.
dexamethasone supression test- if someone has a problem which is increasing cortisol eg adenoma, then the dexamethasone wont be able to reduce the cortisol levels because nothing is working physiologically. Whereas a person who has ok levels of cortisol would have very low levels of cortisol the next day from the dexamethasone.
