growth hormone Flashcards
what stimuli triggers GH release
stress (exercise), low blood glucose (fasting), circadian rhythm (sleep)
what is the hormone released by the hypothalamus (function and target cells in ant. pit)
GHRH (stimulatory) and somatostatin (inhibitory)
target cell: somatotrophs
describe GHRH receptor
GPCR: couples to Gs > stim AC > + cAMP
activation of GHRH receptors >increase growth hormone from intracellular pools
and increased transcription of growth hormone gene
describe somatostatin receptor
GPCR: coupels to Gi > inhibit AC > decrease cAMP
activation > inhibition of growth hormone release
what does ant pit release (name hormone + target)
ant pit releases GH
target liver cells in periphery
liver releases insuline like growth factors IGF-I and II
what does growth hormone do (direct/indirect)
direct effect:
- anabolic effects (increase amino acid uptake and protein synthesis)
- anti-insulin effect: lipolysis, impair glucose uptake, increase gluconeogenesis (oppose action of insulin)
indirect effect: stimulate secretion of IGF-I and II from liver
elaborate on the indirect effect of GH on liver
secret IGFI and II
IGF I > proliferation of chondrocytes (cartilage cells) > bone growth
IGF II > proliferation and differentiation + protein synthesis + increase transcription > growth of other tissues
what negative feed back are present
both GH and IGF produce negative feed bck on hypothalamus
decrease GH production > …..
Decreased GH production may result in dwarfism—can test in children by making then exercise and measuring GH production
elevated GH before puberty/after =>
Elevated GH levels before puberty develop gigantism; elevated GH levels after puberty develop acromegaly
Overproduction may also cause … treated with …
diabetes (anti-insulin effects), and hypertension, heart disease, arthritis, etc.
Octreotide is a somatostatin analog to counteract effects of excessive GH levels
