Pituitary Physiology Flashcards
Control of GH is primarily stimulatory/inhibitory
stimulatory GHRH
Direct tissue effects of GH
decreased insulin sensitivity (elevated BG) lipolysis protein synthesis epiphyseal growth (but less than IGF) production of IGF in liver
GH effect in liver
production of IGF-1
*strange because it has opposing mechanisms to GH, except both cause protein synthesis and epiphyseal growth
IGF-1
synthesis
actions
synthesized in liver in response to GH presence
- acts like insulin –> decreases BG
- protein synthesis
- decreases lipolysis
- epiphyseal growth (greater than GH)
Where is GH synthesized
anterior pituitary
Where is IGF-1 synthesized
liver
Diagnostic test for GH deficiency
insulin-stimulation test
- give insulin with Arg
- decrease in BG
- should cause release of GH to decrease insulin sensitivity
Deficiency in GH leads to…
proportionate dwarfism (disproportionate dwarfism = achondroplasia)
Monitoring of GH Tx in
- children
- adults
children: growth
adults: lipids, fasting Glc, bone density
How does GH affect bones
increases epiphyseal growth in children
causes increased mineralization of bone
ie thickening of bone
Laron syndrome
recessive GH receptor variant
–> insensitive to GH
–> decreased IGF-1, high GH
b/c no feedback mechanism if IGF-1 not present
Pegvisomat
MOA
TU
pegvisomat
MOA: GH receptor antagonist
TU: acromegaly
Cabergoline
MOA
TU
cabergoline
MOA: D2 agonist, inhibits prolactin release
TU: prolactin hypersecretion
Bromocriptine
MOA
TU
bromocriptine
MOA: D2 agonist, inhibits prolactin release
TU: prolactin hypersecretion
How does the hypothalamus primarily regulate prolactin release?
D2 inhibition, if severed then prolactin would constitutively be released
(opposite of other hormones)
