Hypothalamus and Pituitary Flashcards
TRH
from hypothalamus
thyrotropin releasing hormone
stimulates secretion of TSH and prolactin
CRH
from hypothalamus
corticotropin releasing hormone
stimulates secretion of ACTH
GnRH
from hypothalamus
gonadotropin releasing hormone
stimulates secretion of LH and FSH
SRIF
from hypothalamus
somatotropin release-inhibiting hormone
inhibits secretion of GH
PIF
from hypothalamus
dopamine or prolactin inhibiting factor
inhibits secretion of prolactin
dopamine
inhibits secretino of prolactin
GHRH
from hypothalamus
growth hormone releasing hormone
stimulates release of GH
TSH
from anterior pituitary
stimulates synthesis of thyroid hormones
FSH
from anterior pituitary
stimulates maturation of sertoli cells in testes
stimulates follicular development and estrogen synthesis in ovaries
LH
from anterior pituitary
stimulates testosterone synthesis in leydig cells of testes
stimulates ovulation, formation of corpus luteum, estrogen, and progesterone synthesis in ovaries
GH
from anterior pituitary
stimulates protein synthesis and growth
prolactin
from anterior pituitary
stimulates milk production and secretion in breast
ACTH
from anterior pituitary
stimulates synthesis and secretion of adrenal cortical hormones- cortisol, androgens, aldosterone
MSH
from anterior pituitary
stimulates melanin synthesis
oxytocin
from posterior pituitary
stimulates milk ejection and uterine contractions
vasopressin
aka ADH
from posterior pituitary
stimulates water reabsorption in collecting ducts and constriction of arterioles
supraoptic nuclei
ADH neurons
paraventricular nuclei
oxytocin neurons
somatotrophs
release GH
GH release
pulsatile
highest during sleeping
(+) GHRH
(-) somatostatin
IGF-1 maintains negative feedback
IGF-1
levels correlate with GH levels
responsible for many of growth effects of GH and is necessary for chondrocyte differentiation
GH action
stimulates lipolysis, AA into cells, protein synthesis
stimulates production of IGF-1
LH and FSH
released in response to GnRH from hypothalamus
stimulates estrogen/progesterone and testosterone production
stimulate follicular maturation/ovulation and spermatogenesis
GnRH release
pulsatile
frequency determines LH or FSH
high - LH
low - FSH
negative feedback on FSH and LH release
sex steroids on hypothalamus and pituitary gonadotropes
inhibin - on pituitary FSH secretion
prolactin
(+) TRH
(-) dopamine
stimulates dopamine synthesis (- feedback)
ADH
aka vasopressin
maintains osmolality of body fluids and blood volume
(+) increased serum osmolality and decreased presure
osmolality is more sensitive stimulator
hypothalamus hormones
go to anterior pituitary in high concentrations
low concentration in systemic circulation
thyrotropes
release TSH
gonadotropes
release FSH and LH
corticotropes
release ACTH
somatotropes
release GH
lactotropes
release PRL
TSH, FSH, LH family
all glycoproteins
same alpha, different beta
HCG also same alpha, different beta
ACTH family
derived from POMC
MSH found in several of the endopeptidase product from POMC cleavage
addisons disease
adrenal insufficiency
ACTH and POMC levels are increased
skin pigmentation
GH secretion
pulsatile
largest within one hour of falling asleep
stimulation of GH
decreased glucose, FA
fasting, puberty, exercise, stress
stage 3 and 4 of sleep
alpha-adrenergic agonists
inhibition of GH
increased glucose, FA obesity senescence somatostatin GH beta-adrenergic pregnancy
somatostatin
inhibits GH release
(+) GH and somatomedins
actions of GH
linear growth
protein synthesis
carb and lipid metabolism
diabetogenic effect
GH causes insulin resistance and decreases glucose uptake and utilization in target tisues
GH deficiency
failure to grow
short stature
mild obesity
delayed puberty
due to decreased GHRH secretion or primary deficiency of GH from anteiror pituitary
GH excess
most commonly adenoma
- before puberty - gigantism
- after puberty - acromegaly
prolactin
(+) TRH
(-) dopamine
prolactin inhibits its own secretion by stimulating dopamine production
prolactin stimulation
pregnancy and breastfeeding
estrogen/progesterone and prolactin
down-regulate prolactin receptors in breast and block action
E and P high during pregnancy, drop at birth
excess prolactin
galactorrhea and infertility
inhibition of GnRH bc of high prolactine levels
ADH
increase water reabsorption in response to osmolality increase
action of ADH
V2 receptor - increase aquaporin channels in kidneys
V1 receptor - increase TPR with contraction of smooth muscle
central diabetes insipidus
failure to secrete ADH
low ADH levels
large volumes dilute urine
concentrated body fluid
Tx: dAVP
neurogenic diabetes insipius
defective V2 receptors in kidneys
high ADH levels**
large volume dilute urine
Tx: thiazide diuretics - inhibit Na reabsorption in distal tubule
SIADH
syndrome of inappropriate ADH
excess ADH from other site (lung tumor)
high ADH
dilute body fluid
oxytocin
stimulates contraction of myoepithelial cells lining milk duct
major stimulus is sucking nip
milk ejection and uterine contraction
blood supply to posterior pituitary
inferior hypophyseal arteries from anterior pituitary
causes of hypopituitarism
pituitary Dx
hypothalamic Dx
traumatic brain injury
stroke
cortisol
increases blood glucose
spike at 8am
pregnant woman and ischemia?
lose blood
pituitary infarction
sheehan syndrome
pituitary infarction
some cases, posterior pituitary relatively unaffected - bc of different blood supply
causes of hyperprolactinemia
drugs that decrease dopamine
hypothyroidism - increase TRH can increase prolactin release
at birth
prolactin decreases over 2-3 months
increase with breastfeeding
GnRH and prolactin?
increased prolactin suppresses GnRH
all hormones decreased except prolactin?
likely damage to the pituitary stalk
bc hypothalamus release hormones can’t reach anterior pituitary and dopamine can’t reach anterior pituitary to decrease prolactin
low FSH and LH and prolactin high?
high prolactin inhibits gonadotrope release
prolactinoma
increase prolactin levels will inhibit gonadotropin release
Tx: dopamine agonist - to inhibit prolactin release
causes of acromegaly
somatotroph adenoma of anterior pituitary
GHRH release from hypothalamic tumor
GH-IGF axis
GH increases IGF levels
IGF feedback to increase somatostatin - inhibits GH
IGF inhibition - undernutrition, illness, GH receptor deficiency, GHR antibodies, IFG-1 receptor deficiency
GH ad IGF
sometimes uncoupled like during
protein intake
increased GH, IGF, and insulin
carbohydrate intake
decreased GH, increased insulin, ~ IGF-1
increased caloric storage
fasting
increased GH
insulin decrease
decreased IGF-1
increased caloric mobilization
decreased protein synthesis and growth
GH effects
growth
protection of body during stress
IGF-1
more stable in serum, longer half life
better indicator for GH levels
glucose suppression test
to suppress GH
bitemporal hemianopsia
partial loss of visual both fields
often associated with acromegaly
GH and fat, protein, glucose
lipolysis
protein synthesis
increased glucose levels (cause insulin resistance)
high GH and insulin
increased insulin levels - hyperplasia of beta cells
over time - beta cells can start to die-
-beta-cell exhaustion
GH induced diabetes
yes, can happen
like in acromegaly
octreotide
somatostatin analogue
for high GH secretion
pegvisomant
GH receptor antagonists
for high GH secretion
diabeticogenic effect of GH
causes insulin resistance
GH actions
diabetogenic
increased protein synthesis (IGF-1)
increased linear growth (IGF-1)
