pituitary Flashcards
where is the pituitary gland found
pituitary fossa of the sphenoid bone / sella turcica
what does the pituitary gland lie immediately inferior to
optic chiasm
what effect does a pituitary tumour have on the visual field
bitemporal hemianopia
how is the hypothalamus attached to the pituitary gland
pituitary stalk (infundibulum)
what embrylogical structure is the anterior pituitary derived from
Rathke’s Pouch
what are the 3 sections of the anterior pituitary
pars distalis
pars tuberalis
pars intermedia
what is another name for the anterior pituitary
adenohypophysis
what are the 3 cell types in the anterior pituitary
acidophils
basophils
chromophobes
how is the anterior pituitary organised into cells
“islands, cords of cells”
what is prolactin under tonic inhibition from
hypothalamic dopamine
what do basophils produce
corticotrophs - ACTH
thyrotrophs - TSH
gonadotrophs - FSH/LH
paired hormone concept refers to what
the pituitary released hormones (central) that are linked to peripheral hormones
what is another name for the posterior pituitary
neurohypophysis
what makes up the posterior pituitary
pars nervosa
the posterior pituitary is an extension of what
the brain - modified glial cells and axonal processes
what cells make up the posterior pituitary
non-myelinated axons of neurosecretory neurones
what hormones does the posterior pituitary gland release
ADH/vasopressin
OT/oxytocin
where are ADH and OT synthesised
hypothalamus
what are the 2 routes of access to the pituitary fossa
transcranial (under frontal bone)
transphenoidal (via nasal cavities and sphenoid sinus)
what structures are at risk in pituitary gland surgery
optic chiasm/CN II CN III, IV, V VI cavernous sinus ICA dura mater
what would happen if the following was damaged in pituitary gland surgery:
optic chiasm
bitemporal hemianopia
what would happen if the following was damaged in pituitary gland surgery:
CN III
problems with several eye movements
dilated pupil
what would happen if the following was damaged in pituitary gland surgery:
CN IV
medial deviation of the eye
SO damage
what would happen if the following was damaged in pituitary gland surgery:
CN V
sensory symptoms on face
problems chewing food
what would happen if the following was damaged in pituitary gland surgery:
CN VI
problems with abduction of eye
LR damage
what would happen if the following was damaged in pituitary gland surgery:
cavernous sinus
venous haemorrhage
what would happen if the following was damaged in pituitary gland surgery:
ICA
haemorrhage
what would happen if the following was damaged in pituitary gland surgery:
dura mater
CSF leak
what are some examples of anterior pituitary hyperfunction
adenoma
carcinoma
what are some examples of anterior pituitary hypofunction
surgery radiation haemorrhage ischaemic necrosis (Sheehan syndrome) tumours extending into sella inflammatory (sarcoid)
what are some examples of posterior pituitary hypofunction
DI - lack of ADH secretion
what are some examples of posterior pituitary hyperfunction
SIADH
ectopic secretion of ADH by tumours/paraneoplastic/primary disorder in pituitary
what are some examples of posterior pituitary hyperfunction
SIADH
ectopic secretion of ADH by tumours/paraneoplastic/primary disorder in pituitary
do pituitary adenomas more often occur anterior or posterior
anterior
what % of intracranial tumours are pituitary adenomas
10% - relatively common
what can cause a pituitary adenoma
MEN1 or sporadic
what problems can a non-functional pituitary adenoma cause
hypofunction - hypoadrenalinism, hypothyroidism, hypogonadism, DI, GH deficiency
what local effects can a pituitary tumour cause
headache bitemporal hemianopia compression on CN II III IV V VI atrophy of surrounding tissue disturbance of hypothalamic centres of temperature sleep and appetite affected infarction --> panhypopituitarism erosion through floor of sella --> CSF rhinorrhoea
what is the most common functional pituitary adenoma
prolactinoma
what is the 2nd most common functional pituitary adenoma
GH secreting
what would an ACTH secreting pituitary adenoma cause
cushings disease –> bilateral adrenocortical hyperplasia
usually a microadenoma
are pituitary carcinomas common or rare
rare (< 1% pituitary tumours)
are pituitary carcinomas usually non-functional or functional
functional - prolactin or ACTH
do pituitary carcinomas metastasise late or early
late after many recurrences
do prolactinomas present earlier in males or females
females
what are some s/s of prolactinoma in females
galactorrhoea menstrual irregularity/amenorrhoea infertility decreased libido vaginal dryness weight gain
what are some s/s of prolactinoma in males
impotence visual field abnormality headache decreased facial hair galactorrhoea infertility decreased libido
how does increased prolactin cause hypogonadism, infertility and osteoporosis
inhibits secretion of GnRH therefore decreased LH/FSH/Testosterone/oestrogen
what size is a microadenoma and what is a macroadenoma
microadenoma < 1cm
macroadenoma >1cm
what investigations are done in suspected prolactinoma
(pregnancy test) serum prolactin conc MRI pituitary visual fields pituitary function tests to see other hormones affected U+Es
what is the first line treatment in a prolactinoma
dopamine agonist
what are 3 examples of dopamine agonists and what has the least side effects
Bromocriptine
Quinagoldine
Cabergoline (least side effects)
what do dopamine agonists do in prolactinomas
restore menstrual cycle and decrease tumour size
what are some side effects of dopamine agonists
N+V
low mood
postural hypotension
fibrosis of heart valves
which of the dopamine agonists cannot be used in pregnancy
bromocriptine
what is the treatment in prolactinoma if the person is dopamine agonist intolerant
surgery
what does a GH secreting pituitary adenoma cause
acromegaly
are men or women more prone to getting a GH secreting pituitary adenoma
men
why does a GH secreting pituitary adenoma cause acromegaly
GH stimulates IGF-1 which causes growth of bone, cartilage and connective tissue
what are some common phrases that go with acromegaly
“rings and shoes dont fit anymore”
“wonky jaw”
“put on weight (muscle) but now look haggard”
what else is a cause of acromegaly
hyperplasia e.g. via ectopic GHRH form carcinoid tumour (rare)
what are some s/s acromegaly
snoring/sleep apnoea headache thickened soft tissues - skin, large jaw, large hands, sweaty hypertension wide nose big supraorbital ridges macroglossia wide spaced teeth acanthosis nigricans amenorrhoea/reduced libido arthralgia/back ache DM local pituitary effects colon cancer/polyps cardiac failure/early CV death
what investigations are done in suspected GH secreting pituitary adenoma
IGF-1
GTT suppression test
MRI pituitary fossa
look at old photos
blood glucose, Ca, phosphate in acromegaly
raised
what would be normal results of a GTT supression test
GH suppresses to < 0.4 ug/L after glucose
what would be results of a GTT suppression test that indicate acromegaly
GH unchanged/no suppression/paradoxical rise/remains > 1ug
what is the treatment for a GH secreting pituitary adenoma
surgery
radiotherapy if unsuitable for surgery
drugs
what might give false positives in a GTT
puberty pregnancy hepatic and renal disease anorexia DM
what is considered clinically safe levels of GH in follow up of GHSPA
GH < 0.4 (post GTT) or < 2 random
why should random GH measurement not be relied on
normal secretion is pulsatile
what effect do stress, sleep, puberty and pregnancy have on GH secretion
increase
what should be surveillanced after a GHSPA
cancer - colon/tubulovillous
CV risk factors
as a follow up what should people with GHSPA get yearly
GH
IGF-1
+/- OGTT
visual fields
what is the first line drug treatment for acromegaly
somatostatin analogues
give 3 examples of somatostatin analogues
sandostatin LAR
lanreotide
octreotide
what do somatostatin analogues do
reduce GH in most patients and tumour shrinkage in 30-50% of cases in 6-12 weeks - although reexpansion once stopped
what drug is used to relieve headache post op within 1 hour
somatostatin analogue
what are some side effects of somatostatin analogues
local stinging flatulence diarrhoea abdominal pain gall stones impaired glucose tolerance
what other drugs can be used in the treatment of acromegaly
dopamine agonists
GH antagonists
what is an example of a dopamine agonist
cabergoline
when would cabergoline (dopamine agonist) be preferred
tumour that co-secretes GH and prolactin
what is an example of a GH antagonist
Pegvisomant
how is pegvisomant administered
SC
how does pegvisomant work
binds to GH receptor and blocks GH activity
does pegvisomant reduce tumour size
no - may see small increase in some
does pegvisomant decrease IGF-1
yes
GH may rise
where are craniopharyngiomas found
between pituitary and 3rd ventricle floor
what are craniopharyngiomas derived from
pituitary embryonic tissue - remnants of rathke’s pouch
what % of intracranial tumours are craniopharyngiomas
1-5%
are craniopharyngiomas slow or fast growing
slow
how might you describe a craniopharyngioma
may be solid/cystic/calcific/full of debris
are most craniopharyngiomas suprasellar or within sella
suprasellar
craniopharyngiomas have a bimodal incidence
what are the 2 most common age ranges
5-15 years
50-60 years
what is the most common childhood intracranial tumour
craniopharyngioma
what is the prognosis like of a craniopharyngioma if it is < 5cm
excellent
what may develop following radiation treatment
SCC
what are some s/s of a craniopharyngioma
growth retardation in children - > 50% present with this headache / visual disturbance N+V DI behavioural changes early/delayed puberty/oligo/amenorrhoea impotence reduced libido reduced fertility appetite/weight changes sleep disturbance
does pituitary hypofunction usually affect one or multiple hormones
usually panhypopituitarism
what are some s/s of anterior panhypopituitarism
menstrual irregularites/infertility/impotence gynaecomastia decreased strength abdominal obesity loss of facial/axillary/pubic hair dry skin and hair erectile dysfunction hypothyroid growth retardation osteoporosis decreased libido decreased CO and exercise ability
what is an example of posterior hypopituitarism
diabetes insipidus
what can cause panhypopituitarism
tumour
secondary mets (lung breast)
local brain tumour - astrocytoma, meningioma, glioma
granulomatous disease e.g. TB, sarcoidosis, histiocytosis
vascular disease (polyarteriitis)
trauma
hypothalamic disease (syphillis, meningitis)
sheehan syndrome
infection
craniopharyngioma
irradiation of pituitary
infiltration - haemochromocytosis, amyloid
kallmans
how do you check pituitary steroid hormone production
synacthen stimulation test - cortisol
insulin tolerance test (cortisol and GH)
when would you do a prolonged glucagon test instead of an insulin tolerance test
epilepsy
heart disease
adrenal failure
what is a normal cortisol following insulin tolerance test
> 500
what is a normal GH following insulin tolerance test
> 7 ug/L
apart from checking pituitary hormones in panhypopituitarism what else would you want to do
MRI for hypothalamic or pituitary tumour
what is the treatment of panhypopituitarism
replace lost hormones
how would hypothyroidism as a result of panhypopituitarism be treated
thyroxine
how would secondary adrenal failure as a result of panhypopituitarism be treated
hydrocortisone
how would DI as a result of panhypopituitarism be treated
desmospray
how would GH be replaced
nightly SC
how would sex steroids be replaced
HRT/oestrogen/progesterone
testosterone
how can testosterone be given
IM injections, skin gel or tablets
what are 3 side effects of testosterone replacement
prostate enlargement (monitor PRE and PSA)
polycynthaemia (monitor FBC)
hepatitis (only oral tablets)
what is the problem in diabetes insipidus
no ADH secretion to act on kidneys to cause water retention so lots of pure water is lost in urine
what is Na like in DI
high
what are some s/s of hypernatraemia
irritability lethargy cognitive dysfunction tachycardia abnormal skin turgor dry axilla
what are the 2 groups of causes of DI
central and nephrogenic
what is a nephrogenic cause of DI
renal resistance to ADH
what are some central causes of DI
familial (DIDMOAD) - DI, DM, optic atropy, deaf
ADH deficiency
trauma/surgery
tumours
inflammatory disorders of pituitary/hypothalamus
sarcoidosis
meningitis
how is DI diagnosed
water deprivation test
what is another test that should be done when someone presents with the symptoms of DI
serum glucose to exclude DM
describe a water deprivation test
NBM for 8-12 hours
check urine and serum osmolalities for 8 hours then 4 hours after giving IM DDAVP
describe the results of a water deprivation test
Ur/serum osmol ratio > 2 = normal
otherwise - DI
if it improves after DDAVP = cranial DI
what is the treatment of central DI
desmospray
desmopressin (oral or IM) in emergency or post pituitary surgery
what are the s/s of DI
similar to DM
polyuria
polydipsia
dehydration
what is the treatment of nephrogenic DI
bendroflumethiazide
NSAIDs
how do NSAIDs help in nephrogenic DI
lower urine vol and serum Na by inhibiting prostaglandin synthase - prostaglandins locally inhibit action of ADH
in hormone replacement should hydrocortisone or levothyroxine be given first
steroid first - thyroid may ppt as adrenal crisis
what is a pituitary apoplexy
rapid pituitary enlargement from bleed into a tumour which may cause mass effects and hypopituitarism –> CV collapse and death
