Pituitary Physiology Flashcards
what does the posterior pituitary gland secrete
oxytocin and ADH
oxytocin function
allows the milk to be released when women breast feed
where are the posterior pituitary gland secretions formed
- These hormones are synthesized in the body of the nerve cells in the hypothalamus, the gland is an extension of these nerve cells
- Secretions controlled by neurons
describe the formation and storage of ADH
- An octapeptide that is synthesised in the hypothalamus in neuron cell bodies. It is transported down neuron axons to nerve terminal in the posterior pituitary gland, where it is stored in granules.
- It is released into the blood when action potentials down the nerves lead to Ca2+ dependent exocytosis.
what does the anterior pituitary gland secrete
ACTH, TSH, FSH, LH, PRL and STH
what are secretions to the anterior pituitary gland controlled by
inhibitory and releasing hormones - secretions first absorbed by capillaries at the base of the hypothalamus and then to pituitary
gonadotropins
eg LH and FSH
regulate growth, sexual development and normal reproductive function
stimulate production of testosterone and E2 (oestrogen)
E2
estradiol
an oestrogen
steroids - pituitary and peripheral hormones
pituitary - ACTH
peripheral - cortisol
GH - pituitary and peripheral hormones
pituitary: GH
peripheral: IGF-1
suppression test
performed if it is suspected that too much hormone produced
stimulation test
performed if it is suspected that too little hormone is produced
insulin stress test
suspected glucose, cortisol, GH deficiency
involves giving the patient IV insulin to make the hypoglycaemic, this stress should stimulate the hypothalamus and cause glucose, GH and cortisol levels to rise
eg if werent producing GH that curve wouldnt rise
synacthen test
Synthetic ACTH, performed when there is a suspected lack of cortisol
cortisol levels checked at 0, 30 and 60 minute intervals
what test is the gold standard for assessing the integrity of the HPA
insulin stress test
what is a non functioning pituitary adenoma
one that doesnt secrete any hormones
complications of NFPA if extends upwards
compression of optic chiasma - bitemporal hemianopia
complicationsof NFPA if it extends laterally
cavernous system
- CNIII - several eye movements and dialted pupil
- CNIV and CNVI - problems with specific eye movements
CNV (I and II)
internal carotid artery
cavernous sinus
complications of NFPA if it affects the pitutiary
hypo - adrenalism, thyroidism, gonadism
diabetes insipidus if posterior pituitary affected
GH deficiency
difference in size between a micro and macro adenoma
1cm
pituitary carcinoma
rare, and often functional
metastasize late after multiple recurrences
craniopharyngioma
- what is it derived from
- brain tumour derived from pituitary gland embryonic tissue - Rathke’s pouch
- most common childhood intracranial tumour
- most arise in the sella
who do craniopharyngiomas most commonly occur in
children
also adults in 50s and 60s
describe the progression of a craniopharyngioma
slow growing, cystic and may calcify
clinical features of craniopharyngiomas
- presentation in adult and child
over 50% present in children with growth failure
headaches and visual disturbances (compression of optic chiasma)
adults may present with amenorrhoea
investigation of craniopharyngiomas
CT/MRI
treatment and prognosis of craniopharyngiomas
surgery ± post-op radiation
prognosis is excellent, especially if it is <5cm
