Pituitary Flashcards
Effect of somatostatin on GH
Inhibitory
Effect of somatostatin on TSH
Inhibitory
Effect of dopamine on prolactin
Inhibitory
In which 3 places can hypopituitarism be caused?
Hypothalamus, pituitary stalk and pituitary
What is Kallman’s syndrome?
Defect in gene KAL1 involved in making anosmin which is involved in olfactory system and migration of GNRH secreting neurons
Therefore causes GnRH deficiency - and hypogonadism
Also anosmia
What other hypothalamic problems can cause hypopituitarism?
Tumour, inflammation, infection (meningitis and TB) and ischaemia
Pituitary stalk origin of hypopituitarism?
Trauma Surgery Mass lesion (craniopharyngioma) Meningioma Carotid artery aneurysm
Pituitary origin of hypopituitarism?
Tumour Irradiation Inflammation Autoimmunity Infiltration - mets, haemochromatosis, amyloid Ischaemia - pit apoplexy (haemorrhage or infarction of a pituitary tumour) + Sheenhan's syndrome (pit necrosis following postpartum haermorrhage) Skull base fracture Infection - meningitis, encephalitis
What type of tumours are pituitary tumours normally?
Benign adenomas
10% of all intracranial tumours
What are chromophobe tumours?
70% Many are non-secretory Some cause hypopituitarism Half produce prolactin A few produce ACTH or GH
What do acidophil tumours produce?
GH, PRL
What do basophil tumours produce?
ACTH (Cushing’s)
LH, FSH, TSH - rarer
Local pressure effects in pituitary tumours
And hypothalamic effects
Headache,
Visual field defects - bitemporal hemianopia
Palsy of CN III, IV and VI
Diabetes Insipidus (post-pit)
Disturbance of hypothalamic centres of temp, sleep and appetite
If treated hypopituitarism what order do you need to give drugs?
Steroids (to treat Cushing’s) before levothyroxine
As levothyroxine can precipitate an adrenal crisis (addisonian crisis)
What is pituitary apoplexy?
Rapid enlargement of a pituitary tumour due to infarction or haemorrhage.
Can cause sudden severe headache and rapidly deteriorating visual function including double vision and vision loss.
Sometimes followed by acute hypopituitarism
Can be treated conservatively with hormone replacement but if bad visual loss then may need decompressive surgery
Need to give steroids to prevent Addisonian crisis
When give cabergoline?
Dopamine agonist given if prolactinoma
What is a craniopharyngioma?
Not strictly a pit tumour as it originates from Rathke’s pouch of hypothalamus - situated between pituitary and 3rd ventricle floor
Commonest intracranial tumour in childhood
Present with growth failure
But can present at any age - presentation mimics intrinsic pituitary lesion
Often calcified - can see calcification on xray in 50%
Order of deficiencies following pituitary tumour growth?
GH and gonadotropins usually affected first
Hyperprolactinaemia (loss of dopamine tonic inhibition) usually occurs early on as well
Then LH and FSH
TSH and ACTH usually affected last
What is panhypopituitarism?
Deficiency of all pituitary hormones - usually due to tumour, irradiation or surgery
Rarely are post-pituitary hormones affected
Can be if severe suprasellar extension to affect hypothalamus
How does hyperprolactinaemia present in women and men?
Women - usually presents earlier with menstrual disturbance
- can also get galactorrhoea, low libido, weight gain and dry vagina
Men - later as erectile dysfunction or mass effects
- also get galactorrhoea and loss of facial hair
What can raised prolactin levels cause?
Hypogonadism, infertility and osteoporosis
- by inhibiting GnRH production and therefore production of LH and FSH
Causes of hyperprolactinaemia
Prolactinoma (very high prolactin levels likely to be this - >5000mu/L)
Compression of pit stalk
Use of dopamine antagonist
Which endocrine disorder can cause increased prolactin secretion?
Hypothyroidism - increased TRH which stimulates prolactin secretion
Drugs which can cause hyperprolactinaemia
Metoclopramide Haloperidol Anti-psychotics A-methyldopa Oestrogens MDMA/ectasy
