5 HP Axis pt. 2 Flashcards
true or false: TSH is expressed in one unique type of specialized cell
false, it’s released by different cells
GH and PRL are _____
co expressed
where is the largest portion of endocrine cells located?
anterior pituitary
where is GH stored?
in granules
define somatotroph
cells in the pituitary that produce GH (GH is also called somatotropin)
GH is what kind of hormone? lipid or peptide?
peptide
what genes are part of GH’s locus?
hGH-N, hCS (with A, B, V, and L isoforms),
what hCS hormone is expressed by the placenta during midgestation?
hCS-V
what are the 2 isoforms of GH?
22 kDA & 20 kDA
what’s the difference between the 2 isoforms of GH?
there’s not a stark difference but there appears to be a difference in glycosylation and bioactivity. the larger isoform appears to be the predominant one.
what is an application of GH?
treatment of dwarfism
how is GH isolated?
recombinant GH is produced in a bacterial system.
it used to be extracted from 60,000 dead bodies, which was a problem because of prions :0
expand GHRH
growth hormone releasing hormone
what hormones does the hypothalamus release to regulate GH?
GHRH and somatostatin (SRIF)
GHRH is the stimulatory factor
SRIF is an inhibitory factor
what favors the production of SRIF?
look at slide 15
do males or females have a greater response to GHRH?
females
SRIF (induces/inhibits) GH secretion
inhibits
does SRIF regulate GH production?
no
in what life stage is GH levels the highest?
fetus
does a child or an adolescent have more GH levels?
adolescent
how is an increase in GH level achieved? (frequency or amplitude?)
by increasing the amplitude (volume being released), not frequency
expand GHBP
Growth Hormone Binding Protein
GH circulates as a (free/bound) hormone
bound (to GHBP)
true or false: growth hormone receptors have autophosphorylation proteins
false
expand SOCS
suppressor of cytokine signaling
what does SOCS do to GHR?
inhibits GH
what happens when there’s no SOCS?
nothing stops the body from continuing to grow
what is the direct effect of GH?
GH targets cells and directly causes a response (proliferate or differentiate)
what is the indirect effect of GH?
target cells to encourage production of IGF-1 then promotes proliferation or differentiation
when is IGF-1’s effects prominent
childhood and adolescence, not so much during the fetal stage
when does longitudinal growth of bones cease?
when concentration of GH decreases. this causes a fusion of the epiphyses
is GH present in adults?
yeah
list some functions of GH in adults (6)
- optimizes body composition, physical functions (strength/height), and substrate metabolism
- regulates glucose, fat, and protein metabolism
- enhances lipolysis and FA oxidation (application in fasting)
- reduces urea synthesis and excretion (spares proteins)
- inhibits insulin stimulated glucose uptake
- induces insulin secretion
GH seems to have contradictory effect on glucose metabolism. what’s the point?
it depends on context. GH will do what it needs to accordingly
expand IGF
insulin-like growth factor
does GH effect IGF 1 or 2? or both?
only 1.
all cells produce IGF but don’t release into the bloodstream. this classifies them as _____
paracrine
where is IGF-I produced?
liver and body tissues. only liver is endocrine.
role of IGF-II?
fetal development
why are IGFs called that?
they have similar amino acid sequencing to insulin
how do cells locally regulate IGF-I?
binding protein and binding protein proteases. this determines how much IGF is bioavailable.
the more proteases the more free IGF-I available
what’s the main difference between GH and IGF-I receptors?
IGF has autophosphorylation capability
how is GH release regulated? (5)
- balance between GHRH and SRIF
- feedback by IGF-I on pituitary and hypothalamus
- negative feedback by GH
- nervous system (stress, sleep)
- metabolites (low glucose stimulates, high glucose inhibits)
as you age, GH concentration (increases/decreases)
decreases
exercise (stimulates/inhibits) GH
stimulates
psychological stress has a (positive/negative) effect on GH
negative
