GH & PRL - Trachte Flashcards
GHIH (Growth hormone inhibitory hormone) is the same as…..
SOMATOSTATIN
Inhibits GH release
What two hormones are secreted from the hypothalamus in regards to GH?
GHRH
GHIH (Somatostatin)
There are 5 somatostatin receptors…. what kind of receptor are they?
Gi-coupled receptor
Decrease cAMP
Activate K+ channels
Aside from somatostatin what neurotransmitter can inhibit GH release?
Dopamine
What type of receptor is the GHRH receptor?
Gs-coupled receptor
Stimulates adenylyl cylcase
Increases cAMP
What cells in the anterior pituitary produce GH?
Somatotropes
GHBP binds GH in the serum… GHBP also indicates tissue levels of GH receptor… why is that?
GHBP is the ectodomain of the GH receptor, which is solubilized
What type of receptor does GH bind on target tissues?
Cytokine receptor (with tyrosine kinase activity) that activates JAK/STAT second messenger signal transduction pathway
this is how all “growth factor receptors” work!!!!*
What are the final hormones mediating GH Axis effects?
Growth Hormone
IGF-1
What organ produces IGF-1 after being stimulated by GH?
The liver!
How does GH affect serum glucose?
Diabetogenic! Causes hyperglycemia due to decreased insulin sensitivity
How does IGF-1 affect serum glucose?
Hypoglycemia
It has insulin like activity
Is IGF-1 or GH better at stimulating chondrogenesis at epipyseal growth plates in children?
IGF-1
What stimulates GHIH release?
IGF-1 (negative feedback!)
What is Sermorelin?
GHRH analog
What is Laron-type Dwarfism?
GH receptor variant which has weak binding to GH
Results in LOW IGF-1 levels
Autosomal recessive, present at birth
What determines if hypersecretion of GH will result in gigantism or acromegaly?
Determined by timing of epiphyseal plates closure
Hypersecretion in adults - leads to acromegaly
What is the first indication of GH hypersecretion?
Elevated IGF-1
What is the primary treatment for GH hypersecretion?
Somatostatin analogues (Octreotide)
Dopamine Agonists (D2) = Bromocriptine
What is bromocriptine?
Dopamine agonist used to treat GH hypersecretion
What is Octerotide?
Somatostatin analogue used to treat GH hypersecretion
What is Pegvisomant?
Growth Hormone receptor antagonist used to treat GH hypersecretion
**basically binds GHR and is so big, that it doesn’t let the cross phosphorylation happen…. neato!
What is needed for a clinical diagnosis of GH hyposecretion?
GnRH-arginine costimulation test (should raise GH levels)
or
Insulin tolerance test (induces hypoglycemia which should stimulate GH)
What is the primary inhibitory factor for prolactin?
Dopamine! (D2 receptors)
Is prolactin primarily under stimulatory or inhibitory control?
Inhibitory!!
Prolactin releasing hormone is “hypothetical”
What cells produce and secrete prolactin?
Mammotrophs
What happens to prolactin if you block the hypophyseal portal system?
IT GOES UP!!!!! (because it is under inhibition!)
Does prolactin stimulate milk production or secretion?
PRODUCTION!
What kind of receptor is the prolactin receptor?
Tyrosine kinase!
Does prolactin participate in a negative feed back loop?
Nope!
What would you use to treat a hyperprolactinemia tumor?
Dopamine agonists!
Cabergoline
Bromociptine
What is Cabergoline?
Dopamin agonist!
Used to treat hyperprolactinemia tumor
**preferred to other dopamine agonists because it has higher efficacy in normalizing prolactin levels, and higher frequency of tumor shrinkage! NEAT
