Endocrinology 2 Flashcards
what is anterior pituitary made of?
develops from rathke’s pouch (upgrowth of ectoderm from primitive oral cavity)
what is posterior pituitary made of?
..
neural crest origin
anterior pituitary hormones?
FLAT PIG
posterior pituitary hormones?
ADH
oxytocin (squeezes milk out of breast ducts)
anterior pituitary dysfunction phenotype?
relates to hormones which are reduced
often more than one hormone lost and also structural effects of large tumour (adenoma) bulk
tumour in pituitary?
basically all are adenomas
mostly adenoma of one cell type (eg prolactinoma, ACTH producing cells etc)
can also have craniopharyngioma, cerebral and secondary tumours
causes of hypopituitarism?
tumours vascular (sheehans, severe hypotension) infection hypothalamic disorder iatrogenic (radiation, hypophysectomy) miscellaneous (sarcoidosis, haemochromatosis)
hypothalamic disorders?
tumours
functional disorders
isolated deficiency of GNRH and LH/FSH
hypopituitarism usually presents late, when will it present early?
pre-menopausal women as they get amenorrhoea
structural effects of pituitary tumour?
can press on surrounding structures (chiasm ect)
headache
invasion of cavernous sinus
CSF leak due to invasion
effects of tumours pressing on optic chiasm?
bitemporal hemianopia
order in which hormones are lost?
GGAT gonadotrophins GH ACTH TSH
functional effects of pituitary tumour?
loss of normal hormone function - - - -
LH and FSH should be high or low in post menopausal women?
high
if theyre low, might be pituitary problem
biochemistry of hypopituitarism?
measure specific hormones
- TSH and T4 (both would be low)
- LH/FSH (both low)
- oestrogen/testosterone
why arent GH and cortisol useful to measure?
released in pulsatile manner and very variable levels
biochemical tests for hypopituitarism (cortisol and GH)?
hormones are low so try and stimulate them
- make patient hypoglycaemic to stress body and stimulate cortisol production (insulin tolerance test)
imaging in hypopituitarism?
MRI
anterior pituitary deficiency usually involves multiple hormones, is excess the same?
no
how can FSH and LH be measured?
FSH and LH in blood
oestrogen and testosterone in blood
clinical effects of FSH and LH excess?
none really
ACTH excess?
causes excess cortisol production at adrenals (cushings)
symptoms of cushings?
moon face weight gain (central) thin limbs buffalo hump thin hair and skin (poor wound healing) frontal balding aggressive striae diabetes (polyuria) as cortisol is an insulin antagonist hypertension proximal myopathy acne easy bruising osteoporosis oligomenorrhoea headaches insomnia
most common cause of cushings phenotype?
excess steroid medication
other causes of cushings?
tumours/hyperplasia in adrenal cortex
ectopic ACTH
pituitary tumour
cushings biochemistry test?
dexamethasone suppression test (body should recognise extra steroid and switch off cortisol production in normal people)
how is MSH involved in cushings?
anything that increases ACTH also increases MSH production as theyre from the same precursor
features of MSH excess?
pigmentation
in old scars and in buccal mucosa
how is dexamethasone suppression test done?
1mg given at night then early morning blood test next day (cortisol should be <50 in normal people)
- also look at ACTH next day
if cortisol is high but ACTH is low, what does this indicate?
primary adrenal problem
if cortisol not suppressed what other test done??
////
where would you look for a cause if cortisol and ACTH are both high?
pituitary (MRI)
if ACTH ridiculously high then do CXR to look for a malignancy
why is dynamic testing (eg dexamethasone suppression) not needed for thyroid?
hormones are very steady
function of prolactin?
breast milk production
prolactin excess phenotype?
galactorrhoea
gynaecomastia a little (not as much as in oestrogen excess)
loss of libido and erectile dysfunction
amenorrhoea
most common pituitary tumour?
prolactinoma
types of prolactinoma?
micro (<1cm) = benign, doesnt reallt cause problems
macro (>1cm) = tend to grow and can cause problem
how can you tell whether micro or macro?
do MRI 6 months apart and look at growth
what drugs are used in prolactinoma?
dopamine agonists (cabergoline = first line, also bromocriptine and quinagolide)
why is dynamic testing not needed in prolactinoma?
prolactin only present physiologically in pregnancy and lactation
so measuring prolactin levels is enough to detect a problem
why do dopamine agonists work in prolactinoma?
dopamine inhibits prolactin so can shrink the tumour
management of micro vs macro prolactinoma?
all need dopamine agonist
only the macro might need surgery in certain cases
what does GH excess cause?
acromegaly
features of acromegaly?
big hands and feet prominent brow large tongue prominent jaw spacing between teeth can get hepatosplenomegaly can get large heart bone overgrowth causing premature arthritis sweating diabetes hypertension polyps (need to screen for cancer)
what happens if theres GH excess before epiphyseal fusion in childhood?
giantism
biochem test for acromegaly?
need dynamic testing
glucose tolerance test (should suppress GH in normal people)
can also measure IGF-1 which is more stable
imaging for GH excess?
pituitary MRI
management of pituitary adenoma?
prolactinoma = medical
trans sphenoidal surgery for others
radiotherapy can be used to debulk if surgery doesnt get it all
too much ADH?
SIADH
too little ADH?
diabetes insipidus
types of diabetes insipidus?
cranial
nephrogenic (kidney cant respond to ADH)
how does ADH work?
goes to kidney >distal convoluted tubule > attracts aquaporin 2 channels to the membrane to allow water resorption
works via cAMP
diabetes insipidus phenotype?
polyuria (clear urine)
polydipsia
how is diabetes insipidus diagnosed?
water deprivation test (ADH v difficult to measure)
dont allow them to drink between 8am and 4pm and continuously measure blood and urine osmolality (urine will stay dilute and blood will increase osmolality)
then at 4pm give artificial ADH (urine will immediately concentrate in cranial DI)
diabetes insipidus bloods?
high osmolality (disconnect between high osmolality blood but still dilute urine)
psychogenic DI?
excessive water drinking which eventually flushes out concentration gradient in kidney?
management of cranial DI?
ADH/vasopressin
titrate dose to plasma sodium level and symptoms
management of nephrogenic DI?
difficult
correct reversible causes (hyperkalaemia, hypercalcaemia, stop lithium)
massive doses of ADH can sometimes help
generally just need to drink loads and loads
causes of SIADH?
neoplastic pulmonary infection CNS problems drugs (too much desmopressin, some psychiatric drugs) idiopathic hereditary
how is SIADH diagnosed?
low plasma osmolality
high urine osmolality
SIADH phennotype?
confusion
lethargy
nomovolaemic
symptoms of underlying cause
biochem of SIADH?
low plasma sodium
low plasma osmolality
inappropriate high urine osmolality
inappropriate high urine sodium
how is SIADH managed?
water restriction (1-1.5L per day)
not pleasant for patient
if fluid restriction doesnt work, can use demeclocycline (uncouples aquaporin 2 receptor)
tolvaptan (V2 receptor antagonist allows free water excretion)
why dont diuretics work in SIADH?
also cause loss of sodium etc therefore there is no change in osmolality
