Growth Hormone (lec 22) Flashcards
Anterior Pituitary: route of hormones to and from?
hormones down axons @ median eminence ->
neurocrine release into local circ ->
ant pit -> endocrine release
Ant Pit secretor cell types? (5)
1) Somatotroph (45%) (GH)
2) Lacto/Mammotroph (PRL)
3) Corticotroph (ACTH, β-lip)
4) Gonadotroph (FSH, LH)
5) Thyrotroph (TSH)
Growth Hormone synthesis?
Larger preprohormone -> secretory granules Δ/store GH -> bind to protein for circulation
Growth Hormone Releasing Hormones (GHRH):
type of hormone?
role in GH synth?
peptide hormone
act on Gs receptor in somatotrophs -> activates AC/cAMP/Ca2+ release -> release GH from secretory granules
Somatostatin (SS): type of hormone?
role in GH synth?
neuropeptide
binds Gi receptor in somatotrophs -> inhib AC/cAMP/Ca2+ release -> GH release inhibitied
Direct effect of GH?
Indirect effect of GH?
Maintain plasma glucose
growth
GH direct action: protein metabolism?
Anabolic:
↓ glucose uptake -> ↑ AA uptake -> protein synth -> ↑ skeletal mm
GH direct action: carb metabolism?
Glucose-sparing:
↓ glucose uptake by mm, liver, fat ->
↑ gluconeogenesis -> glucose output from liver ->
↑ overall glucose
GH direct action: lipid metabolism?
Lipolytic:
activates trigly breakdown -> FFA release
GH indirect action: Insulin-Like Growth Factor (IGF)
Generated where?
Type of hormone?
Type of action?
liver generates IGF-1
peptide hormones
auto/para/endocrine actions
IGF action on growth?
↑ AA uptake/protein synth in long bone growth plates
Promotes hyperplasia/hypertrophy of organs
Review Slide 22
GH regluation
IGF-1 negative feedback action:
inhibits?
IGF-1 inhibits:
GHRH release from hypothal and
GH release from ant pit
IGF-1 negative feedback action:
stimulates?
SS release from hypothal
GHRH neg feedback action?
inhibits own release at hypothal
