pituitary disease (see DM) Flashcards
(67 cards)
where is the pituitary gland located anatomically
it sits in a saddle-shaped bony cavity of the sphenoid bone, known as the sella turcica; The optic chiasma lies directly superior to the anterior pituitary
what can suprasella extensions of the pituitary gland result in
bitemporal hemianopia (compression of the optic chiasm)
what strucutre can parasella extensions of the piuitary gland affect
cavernous sinus
what is the appearnace of the posterior pituitary gland on an MRI
bright spot posterior to the ant pituitary - it is physiologically hyperdense; there should be no bright spot in the anterior pituitary
what is the anatomy of the posterior pituitary gland (2)
- direct extension of the hypothalamus
- The posterior lobe is connected to the median eminence of the hypothalamus by the pituitary stalk (also known as the infundibulum)
how does the posterior pituitary gland release hormones
- Neurosecretory cells in the hypothalamus synthesise hormones that are transported along axons that terminate in the posterior pituitary
- hormones are then released into capillaries within the posterior pituitary gland to affect body parts directly
how are hormones released from the anterior pituitary
hormones are secreted from the hypothalamus and travel via hypophyseal portal vessels to the anterior pituitary, where they regulate the release of anterior pituitary hormones into the blood
what is the embryological origin of the posterior pituitary gland (3)
- the infundibulum of the diencephalon which grows inferiorly - This is composed of neuroectoderm and forms the neurohypophysis
- The neurohypophysis is therefore in direct communication with the hypothalamus
- Axons from neurosecretory cells in the hypothalamus grow inferiorly into the pituitary stalk and terminate in the posterior pituitary gland
what is the embryological origin of the anterior pituitary gland (3)
- An outgrowth of the primitive oral cavity known as Rathke’s pouch, which grows superiorly -This is composed of ectoderm and forms the adenohypophysis
- The anterior pituitary is not in direct contact with the hypothalamus
- As the connection to the primitive mouth is lost, nests of epithelial cells may be left behind -> Occasionally these cells are functional and secrete ectopic hormones (e.g. craniopharygioma) but are usually benign
what hormones are not under -ve feedback control
- prolactin
- oxytocin (+ve feedback)
why does prolactin not have a feedback loop
no mediator gland
why are FSH levels high in menopause
oestrogen levels are low and so FSH increases to try and compensate
what should be checked in a pt w a hx of fainting and salt craving
cortisol and ACTH levels (addison’s disease) - low cortisol high ACTH in compensation
what hormone should be checked if acromegaly is suspected
IGF-1 (related to GH)
what is the new name for diabetes insipidus
Arginine Vasopressin Deficiency/resistance
what inhibits prolactin
dopamine
what does somatostatin inhibit
growth hormone
how can the pituitary gland malfunction (3)
- gland enlargement/ tumour with local effects
- gland stops working
- gland becomes overactive
what will compression of the cavernous sinus present with
facial pain
signs of pituitary gland enlargement/tumour (4)
- headaches (increased pressure)
- LOC/fits (increased pressure)
- facial pain
- optic involvement(e.g. bitemporal hemianopia, optic atrophy)
what does a supra+paracellular extension look like on an MRI
“snowman” appearance around midline inferiorly (coronal view)
what can cause the pituitary gland to stop working (8)
- non functioning pituitary tumour
- apoplexy
- hypophysitis
- empty sella
- other parasellar cysts/tumours
- post surgery/ radiotherapy/ cancer treatment
- post brain injury or hypotension (e.g. Sheehan’s)
- congenital/genetic
what is Sheehan’s syndrome
postpartum hypopituitarism caused by necrosis of the pituitary gland -> usually the result of severe hypotension or shock caused by massive hemorrhage during or after delivery;
may lead to continued amenorrhoea postpartum or infertility
causes of hypopituitarism (11)
- isolated deficency of pituitary hormones (e.g. Kallmann’s syndrome)
- Pit-1 deficency
- infective (e.g. basal tb, syphilis)
- vascular (e.g. pituitary apoplexy, carotid artery aneuyrsms)
- immunological (piuitary antibodies)
- neoplastic - mostly benign (e.g. carniophayngioma, hypothalmic tumour, glioma etc.)
- traumatic (e.g. skull fracture at base, surgery)
- infiltrations (e.g. sarcoidosis, hypophysitis)
- radiation damage
- empty sella syndrome
- functional (starvation, anorexia, emotional deprivation)
