CEP WK5 - pituitary Flashcards
PITUITARY ANTERIOR LOBE SECRETION
ACTH, FSH/LH, prolactin, GH, TSH
PITUITARY POSTERIOR LOBE SECRETION
ADH & oxytocin
PITUITARY GLAND
connected to hypothalamus by infundibulum & is in bony cavity of the brain
ANTERIOR LOBE
- neurosecretory neurones go through arterial blood from hypothalamus to anterior pituitary (released in venous blood)
- can’t synthesise & secrete own hormones (like pituitary can)
POSTERIOR LOBE
neurones go down (through stalk - from SON & PVN) & reach posterior lobe where they secrete products (it is pretty much just a neural extension of hypothalamus)
GH
- regulated by GH releasing hormone (excites) & somatostatin (inhibits)
- promotes IGF-1 production in liver (leads to growth, glucose metabolism)
- stimulated by hypoglycaemia & has many peaks & troughs in the day
FSH/LH
- regulated by gonadotropin releasing hormone (GnRH)
- in testes (testosterone production) & ovaries (oestrogen release)
PROLACTIN
- regulated by dopamine (inhibits)
- suppresses GnRH (leads to low LH/FSH) & used for lactation
ACTH
- regulated by corticotropin releasing hormone
- high levels in morning & should be undetectable during sleep
- secreted in anterior, goes to adrenal & secretes cortisol (stress, regulate metabolism)
- adrenals deprived of ACTH look small but adrenals with excess look large
ADH
- opens aquaporins to allow water release
- low circulation volume = more ADH released = water excretion = water retention
OXYTOCIN
contraction of smooth muscle of breast & uterus (synthetic oxytocin can induce labour)
GH deficiency
- poor growth, higher abdominal fat
- diagnosed by GH stimulation (injectc insulin to lower glucose as GH stimulated by hypoglycaemia) & treated by hormone replacement
FSH/LH deficiency
- in children, leads to delayed puberty
- in males, leads to infertility & poor 2nd sex features
- in females, leads to low sex drive
- treated by hormone replacement
ACTH deficiency
- fatigue, weakness, weight loss, nausea/vomiting
- diagnosed by measuring morning cortisol (higher in morning)
HYPOPHYSEAL PORTAL VESSELS
where neurotransmitters (from hypothalamus to pituitary) are secreted into
HOW ADENOMA LEADS TO BLURRED VISION
adenoma compresses optic chiasm (which is superior to the pituitary)
TSH deficiency
- TSH usually goes to thyroid & promotes secretion of thyroid hormones
- fatigue, weakness, anorexia, nausea
- diagnosed by measuring TSH & treated by hormone replacement (levothyroxine)
ADH deficiency
- caused by tumours, autoimmune destruction of secretory cells, trauma
- leads to polyuria which leads to thirst (treated by ADH analogues)
- diagnosed by measuring urine output, blood glucose, urine deprivation test (deprive patient of fluids & see if they continue urine output)
ACROMEGALY
- larger hands/feet, headache, more sweating
- GH hyper-secretion due to pituitary adenoma
- diagnosed by checking IGF-1 & doing oral glucose test (give glucose tablet & check GH level as high blood glucose breaks down GH)
- treated by pituitary surgery, GH receptor antagonists
HIGH PROLACTIN LEVELS
- caused by prolactinoma (benign tumour hypersecreting prolactin) which leads to hypogonadism (low FSH/LH)
- diagnosed by pituitary imaging
- treated by dopamine agonist (as dopamine inhibits prolactin secretion) or surgery
CUSHING SYNDROME
- excess cortisol leading to weight gain, fatigue, infection risk
- ACTH-dependent (due to pituitary tumour hyperproducing cortisol) (cushing disease) or ACTH-independent (due to steroid administration)(cushing syndrome)
- measure 24hr cortisol level (should be 0 at night) OR give dexamethasone (steroid which lowers cortisol level in patients without cushing)
- treated by pituitary surgery
ANATOMICAL POSITION OF PITUITARY
- sits in sella turcica
- anterior is sphenoid sinus
- posterior is dorsum sellae (posterior wall of sella turcica)
- superior is optic chiasm & diaphragm sellae (fold of dura mater which covers pituitary gland
ANTERIOR PITUITARY ANATOMY
- split into pars anterior (large & for hormone secretion) pars intermedia (separates pars anterior from posterior lobe) pars tuberalis (surrounds anterolateral of infundibulum)
ANTERIOR PITUITARY VASCULATION
receives arterial supply from superior hypophyseal artery
POSTERIOR PITUITARY VASCULATION
infundibulum & posterior pituitary receive blood supply from many arteries (superior hypophyseal, infundibular artery & inferior hypophyseal)