pituitary disease Flashcards
where is the pituitary gland located
dangles down from the hypothalamus and sits in the sella turcica of the sphenoid bone
what hormones are stored in the posterior pituitary
ADH and oxytocin
what does ADH do
acts to increase water reabsorption by increasing expression of aquaporin channels in the kidney in response to increase serum osmolarity (as a result of decreased water body)
what does oxytocin do
aids in the stimulation of uterine contraction and ejection of breast milk during breast feeding
which hypothalamic hormone is involved in the thyroid axis
TRH
which hypothalamic hormone is involved in the steroid axis
CRH
which hypothalamic hormone is involved in the growth axis
GHRH
which hypothalamic hormone is involved in the prolactin axis
dopamine
which hypothalamic hormone is involved in the sex axis
GRH
which pituitary hormone is involved in the thyroid axis
TSH
which pituitary hormone is involved in the steroid axis
ACTH
which pituitary hormone is involved in the growth axis
growth hormone
which pituitary hormone is involved in the prolactin axis
prolactin
which pituitary hormones are involved in the sex axis
FSH and LH
what is the target hormone for the thyroid axis
T3/T4
what is the target hormone for the steroid axis
cortisol
what is the target hormone for the growth axis
IGF1
what are the target hormones for the sex axis
testosterone, oestrogen and progesterone
what makes prolactin unique (2)
- it is the only one with no target hormone
- dopamine provides negative control over prolactin release, whereas all of the other hypothalamic hormones stimulate the anterior pituitary
hypopituitarism causes
can be isolated to a specific hormone or involve a complete lack of pituitary hormones (pan-hypopituitarism)
hypothalamus causes
- tumour
- infection (TB, meningitis, syphilis)
- genetic (Kallman syndrome, which is isolated deficit of gonadotrophs, associated with absent smell and colour blindness)
pituitary stalk causes
- surgery
- trauma
- carotid artery aneurysm
- tumour (meningioma, craniopharyngioma)
pituitary causes
- irradiation
- non-functioning adenoma
- infiltration (haemochromatosis, amyloid, sarcoid)
- ischaemia
what is Sheehan syndrome
pan hypopituitarism due to pituitary ischaemia and necrosis following a post-partum haemorrhage
Sheehan syndrome presentation
ischaemia due to bleeding of pituitary tumours
hypopituitarism presentation
- lack of CRH (adrenal insufficiency)
- absent TSH (hypothyroidism)
- absent GHRH (central obesity, atherosclerosis, weakness, loss of balance)
- lack of GRH in females (amenorrhoea, reduced fertility/libido, breast atrophy)
- lack of GRH in males (erectile dysfunction, reduced libido, reduced muscle bulk, hypogonadism)
- low blood pressure, can’t lactate if pregnancy, no response to stress
hypopituitarism diagnosis
- static tests: TSH, T3/T4, FSH, LH, testosterone, IGF-1, prolactin
- short synacthen: adrenal axis and ACTH
- insulin tolerance test: adrenal and GH axis (should rise in the presence of hypoglycaemia induced by giving insulin)
hypopituitarism management
- find and treat underlying cause
- manage any hormone deficiencies
what size is a microadenoma
< 10 mm
what size is a macroadenoma
> 10 mm
most common pitutiary tumour
prolactinoma
pituitary tumour presentation
- headache
- visual field disturbance (bitemporal hemianopia due to compression of optic chiasm)
- hormone symptoms (vary depending on hormone secreted/absent due to tumour)
pituitary tumour diagnosis
- hormone tests
- MRI brain
pituitary tumour management
- trans-sphenoidal surgery and possible radiotherapy
- appropriate hormone replacement or antagonism
craniopharyngiomas are most common in
5-15 years old, then 60-70 years old
what is a craniopharyngioma
- not strictly pituitary tumour
- tumour of Rathkes pouch (where pituitary originates)
craniopharyngioma presentation in children
growth retardation
craniopharyngioma presentation in adults
local mass effect or pituitary dysfunction (usually diabetes insipidus)
craniopharyngioma diagnosis
- hormone tests
- MRI brain
craniopharyngioma management
- trans-sphenoidal surgery and possible radiotherapy
- appropriate hormone replacement or antagonism
hyperprolactinaemia physiological causes
- pregnancy
- breastfeeding
- stress
hyperprolactinaemia pathological causes
- hypothyroidism
- pituitary tumour (prolactinoma)
- compression or damage of pituitary stalk (trauma, surgery, tumour)
hyperprolactinaemia pharmacological causes
- anti-emetics (metoclopramide, domperidone)
- anti-psychotics
hyperprolactinaemia female presentation
- galactorrhoea
- reduced libido
- amenorrhoea
- oligomenorrhoea
- infertility
hyperprolactinaemia male presentation
- erectile dysfunction
- reduced facial hair
- galactorrhoea
- men tend to have less prominent galactorrhoea and present later, so more likely to experience pressure symptoms from tumour
hyperprolactinaemia diagnosis
- bloods: TFTs, prolactin, pregnancy test
- MRI brain
hyperprolactinaemia management
- stop any dopamine drugs
- 1st line: dopamine agonists (cabergoline, bromocriptine)
- 2nd line: surgical excision of tumour
acromegaly causes
- caused by overproduction of growth hormones in adults, with the resultant disease (gigantism) seen in children
- most cases caused by GH secreting pituitary tumour (may develop as part of MEN 1)
acromegaly presentation
- growth of hands, feet, lower jaw, brow and tongue
- spade like hands and feet
- tongue gets almost too big for mouth so can struggle to communicate
- coarsening of facial features and widening of nose
- headache, fatigue, sweating, weakness, arthralgia, reduced libido, amenorrhoea, snoring, thick skin
- frontal bossing
- symptoms of hypopituitarism or pituitary tumour (headache, bitemporal hemianopia)
acromegaly complications
- diabetes (because GH is an insulin antagonist)
- malignancy (bowel cancer)
- hypertension, LV hypertrophy and failure, increased risk of ischaemic heart disease, cardiomyopathy
- prone to arthritis in joints due to overgrowth e.g. knees
- hepatosplenomegaly due to over-growing of organs
- increased mortality
acromegaly diagnosis
- bloods: increased glucose, calcium, PO4, high GH/IGF1 levels
- glucose tolerance test (gold standard in diagnosis, should be done if GH/IGF1 levels are high, trying to suppress GH which can’t be done in acromegaly)
- imaging: MRI pituitary
acromegaly first line management
surgical excision of pituitary tumour and possible radiotherapy
acromegaly second line mangement
- somatostatin analogue (octreotide, sandostatin)
- dopamine agonist (cabergoline)
- GH antagonist (pegvisomant)
describe the role of somatostatin analogues in acromegaly management
- somatostatin is the natural analogue of GH, with the analogues serving to reduce secretion by providing negative feedback and blocking peripheral action
- almost immediately relieve headache but take up a year to work
- able to shrink tumour
- side effects include GI upset and gallstones
describe the role of dopamine agonists in acromegaly management
suppress GH secretion but not curative
describe the role of GH antagonists in acromegaly management
- block peripheral action of GH
- don’t shrink tumour
what is diabetes insipidus
- passage of large volumes (> 3l) of water per day
- can occur due to either reduced secretion of ADH or impaired response of the kidney to ADH
central diabetes insipidus causes
- occurs due to failure to secrete adequate amounts of ADH
- idiopathic (most common), genetic, sarcoidosis, pituitary tumours, trauma to pituitary stalk
nephrogenic diabetes insipidus causes
- occurs due to kidney’s response to ADH becoming impaired
- genetic, CKD, lithium, low potassium/high calcium
diabetes insipidus presentation
- dehydration
- polydipsia
- polyuria (extremely excessive, all consuming)
diabetes insipidus diagnosis
water deprivation test
- with assessment of urine osmolarity will indicate if body is able to concentrate urine, if not then diabetes insipidus can be diagnosed (osmolality > 600 is indicative)
- two types can be differentiated by giving ADH and rechecking urine osmolarity, with concentration of urine being seen in central, but not nephrogenic
central diabetes insipidus management
desmopressin (synthetic ADH)
nephrogenic diabetes insipidus management
thiazide diuretics (generate hyponatraemia and drive water reabsorption)
