15. Pituitary Structure/Function Flashcards
two things that hormones do at their target organs?
- stimulate secretion of the effector hormone
- maintain the weight of the target organ. if a gland is deprived of hormone, it will atrophy
inhibiting and releasing factors from the hypothalamus reach the anterior pituitary how?
via capillaries. (portal bed, traverses the capillary stalk). serves to concentrate these factors sufficiently to affect their targets in the pituitary.
what are the 6 hormones from the hypothalamus that affect the anterior pituitary?
CRH, GnRH, GRH, somatostatin, TRH, dopamine
what hormones released from the anterior pituitary are glycoprotein hormones? what do they all have in common?
FSH, LH, TSH (CG)
ALPHA subunit is identical for all
what is HCG? what part of it do we assay for when doing a lab test?
human chorionic gonadotropin (released by placental tissue, indicates preg). probe for the BETA unit because the ALPHA unit of glycoprotein hormones are all identical.
can we detect the hypothalamic releasing/inhibiting hormones in the periphery?
no, too dilute
what are the effector hormones released from the posterior pituitary?
ADH, oxytocin
where are ADH and oxytocin synthesized?
hypothalamic nuclei
if the pituitary were removed, would we have trouble with anterior pit hormones? post pit hormones?
only with anterior pit hormones. the pituitary is only a storage depot for post pit hormones, can do fine without it.
how are hormones transported from the hypothal to the posterior pituitary?
via axonal transport. not capillaries, no portal circulation
what are the two general categories of problems that can result from the pituitary?
- neuro issues due to mass effect
- endocrine issues due to over/under hormone aounts
if the pituitary expands superiorly, what structures are likely to be damaged? what symptoms?
- tentorium sella, through which the pit stalk passes, is highly innervated. stretching will –> headache
- big superior extension -> optic chiasm, bitemporal hemianopsia
- will yield hormonal issues, esp loss of satiety due to the presence of leptin receptors here. -> hypothalamic obesity and temp dysregulation
if the pituitary expands laterally, what structures are likely to be damaged? what symptoms?
- cavernous sinus structures (both loops of carotid artery. no risk of stroke but makes pituitary surgery risky
- CN 3, 4, 6 –> conjugate gaze problems, diplopia
- CN V (maxillary): not affected bc too far inferior
- medial temporal lobes: characteristic seizures w olfactory aura
if the pituitary expands inferiorly, what structures are likely to be damaged? what symptoms?
-floor of sella, sphenoid sinus. consequence: if erosion through this struct, open connection between brain/CSF and the nasopharynx. risk for meningitis.
what is a sx that a pituitary tumor has caused erosion of the floor of the sella?
CSF rhinorrhea
how does the post pit appear w MRI?
bright white spot: for some reason lights up due to presence of ADH.
what ventricle is just superior to the optic chiasm?
third ventricle
hormones involved in the HPA axis?
CRH ->POMC/ACTH->adrenal glands.
3 parts of the adrenal glands, and hormones each produces?
z. glomerulosa -> mineralocorticoids
z. fasiculata -> glucocorticoids
z. reticulata -> sex steroids
what is an example of a mineralocorticoid?
aldosterone
what part of the adrenal gland is not reliant on ACTH?
z. glomerulosa (mineralocorticoids)
what is an example of a glucocorticoid?
cortisol
what adrenal hormone provides feedback to the hypothalamus?
only cortisol/glucocorticoid
a patient with hypoadrenalism from lack of ACTH will be deficient in what hormones?
sex hromones, glucocorticoids. mineralocorticoid (aldo) will be ok
