GH IGF axis
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25 Terms
state 2 facts about GH
a peptide hormone that is 191 amino acids long, called somatotrophin in animals
where is GH produced?
in the anterior pituitary
which 2 factors regulate GH production?
GH releasing hormone and GH inhibitory hormone
in what frequency is GH released into blood?
in pulses
what regulates GH release?
GHRH and somatostatin
what is the main target tissue of GH?
the liver
what is the main response to GH?
increased synthesis and expression of IGF1
How do IGF1 and 2 differ with regards to GH?
IGF1 is GH-dependent, IGF2 is not regulated by GH.
which hormone receptor does IGF1 mimic?
insulin
state 3 cellular effects of IGF1 and 2
potent mitogens, inhibit apoptosis, stimulate differentiation
state 2 metabolic effects of IGF1 and 2
increased amino acid and glucose uptake, increased protein synthesis and decreased protein degradation in many tissues.
how many IGFBPs are there?
6
what occurs when excess GH is produced?
rapid growth
state the difference between gigantism and acromegaly
gigantism occurs before puberty so growth is proportionate; acromegaly occurs after puberty so growth is disproportionate.
state 2 treatments for excess GH
surgery if tumourous, alternative treatments.
state 3 alternative treatments for excess GH
somatostatin analogues, GH antagonists, dopamine agonists
state 2 treatments for GH deficiency
GH injections, gene therapies
what does a high carbohydrate and protein diet lead to?
increased plasma IGF1 and growth
what was IGF2 originally considered?
the foetal IGF
which IGF is high in foetal blood?
IGF2
which IGF is highest in adult blood?
IGF1
after infancy what does a cortisol surge initiate with regards to hepatic expression?
GHR and IGF1 increased expression, reduced IGF2 expression
how do glucocorticoids and thyroid hormones relate to hepatic GHR expression?
they increase or initiate it
how does liver sensitivity change between pre and post natal endocrinology?
increased GH sensitivity
when do plasma IGF1 levels peak?
puberty