Pituitary Flashcards
Hypothalamus
part of the brain that stimulates tropin releasing hormones
Pituitary
anterior: synthesizes stimulating hormones
posterior: stores hormones from hypothalamus for release
TRH
thyrotropin-releasing hormone
CRH
corticotropin-releasing hormone
GnRH
gonadotropin-releasing hormone
ADH or AVP
vasopressin
Anterior pituitary cells & secretions
lactotrophs- secrete prolactin somatotrophs - secrete growth hormone thyrotrophs - secrete thyroid stimulating hormone corticotrophs - secrete ACTH gonadotrophs - secrete LH & FSH
short feedback loop
hormone back to pituitary
long feedback loop
hormone back to hypothalamus
ultra short feedback
feedback between pituitary & hypothalamus
hormone secretions
pulsatile secretions - pulse frequencies
cyclic nature or diurnal variations of hormones : nervous system regulates through signals the circadian/ diurnal variations of hormones
trophic hormones
affect another endocrine gland
TSH, FSH, LH, ACTH
direct effector hormones
act directly on peripheral tissues
growth hormone & prolactin
Growth hormone general
‘somatotropin’ takes up 1/3 of pituitary space
average pulse interval : 2-3 hours
both anabolic & catabolic hormone
Growth hormone peak
occurs at onset of sleep in adults
Growth hormone & insulin
growth hormone is an antagonist of insulin
GH & liver metabolism
promotes gluconeogenesis in the liver & lipolysis for cell energy ( since insulin is inhibited)
what amplifies GH action ?
Insulin-like growth factor 1 or IGF-1
GH deficiency during childhood
dwarfism
GH excess in childhood
gigantism
GH excess in adults
acromegaly: hand & feet enlargement, glucose intolerance, hypermetabolic condition, accelerated atherosclerosis
GH assay methods
assay for IGF1 &/or IGF-1 binding protein to assess GH levels
if liver tumor & cannot use IGF-1 –> test GHRH or L-arginine stimulation & measure GH using immunoassay
FSH, LH, TSH similarities
all are glycoprotein hormones
share same alpha unit
beta unit is hormone specific
FSH in females & males
females: follicle growth (estrogens)
males: produce sperm
LH in females & males
females: stims corpus luteum development (progesterone)
males: produce testosterone
TSH
stimulates thyroid gland to release T4 & T3
ACTH
preadrenocorticotropic hormone formed as active hormone
stimulates adrenal cortex
regulated by CRH & cortisol feedback to hypothalamus
precursor to ACTH
proopiomelancortin
ACTH cyclic nature
high at 8 am & low at midnight
Prolactin
direct effector hormone (similar to GH)
TRH & estrogens can stimulate prolactin release as well as stress, suckling, & exercise
function: effect lactation
Prolactin inhibitor
Dopamine
most common functional pituitary tumor
prolactin secreting tumor
what tests should always be done in conjunction with testing for prolactin
thyroid panel to eliminate hypothyroid cause for symptoms
assess other pituitary hormones to see if they are functioning or not
Posterior pituitary
stores oxytocin & vasopressin (ADH)
Oxytocin
role in lactation, major role in labor & formation
affects pituitary, renal, cardiac, & immune function
can use synthetic oxytocin to induce labor (pitocin)
ADH
peptide hormone that stimulates collecting tubes to increase reabsorption of water & regulates water balance
leads to concentration of urine solutes
Insufficient ADH seen in :
diabetes insipidus - excess thirst & excess urine excretion
Excess ADH seen in :
SIADH - syndrome of inappropriate ADH release
how does ADH affect clotting
promotes factor VII release from liver & vWF release from endothelium cells
Osmotic threshold for vasopressin
284 mOsm/kg
vasopressin baroreceptors located?
carotid arteries, aortic arch & left atrium
2 classes of hormones
steroids & proteins
steroids: cortisol, aldosterone, estrogens, androgens
proteins: insulin, TSH, LH, FSH
steroid hormone chemical make up & cellular actions
chemical make up: cholesterol based
intracellular: interact directly with the DNA to promote cellular response
transport: bound to proteins
protein hormone chemical make up & cellular action
chemical make up: peptide based
intracellular: protein binds to receptor, stimulates G prtoein & then stimulate cyclic AMP to cause response in cell
transport: free
the highest concentration of ____ is found in the pituitary
- PRL
- FSH
- Oxytocin
- Growth hormone
growth hormone!