Lecture 17: Growth Hormone Flashcards
what is the long-term controller of GH secretion
long term nutritional state, particularly protein nutrition
what is the primary regulator of GH release
Somatostatin
hypothalamic signaling of pituitary somatotrophs involved what two opposing trophic hormones
GHRH binds Gs protein coupled receptor
GHIH(somatostatin) binds Gi protein coupled receptor
how is GH synthesized?
using a pre-prohormone mRNA as the template
GHRH (GH releasing Hormone) is secreted from where
medial preoptic area (POA) and the arcuate/infundibular nucleus of the hypothalamus
what inhibits the release of GHRH
emotion, stress, trauma
what increases release of GHRH
catecholamines, dopamine, serotonin
indirect effects of GH
stimulates liver to promote growth positive effects via insulin like growth factor (IGF-1, (somatomedin)
Direct effects of GH
Directly effects intermediary fuel metbolism by binding the growth hormone receptors in tissue
GH effects on blood glucose
decreases glucose uptake by muscles
increases glucose sparing
GH effects on fatty acids
increases lipolysis
GH effects on amino acids
increased uptake of aas into cells
decreases blood amino acids
GH effects on muscle protein
increases protein synthesis
decreases protein degradation
increases RNA and DNA synthesis
GH facilitates insulin action to ….
promote growth
in a fed state, when protein and E intake are ample, protein _______ is favored
synthesis
in a fed state, when carbohydrates alone are consumed, ________ is favored
E storage
hyperglycemia suppresses ________ release while ______ is released to promote the storage of CHOs
GH, insulin
during fasting states, glucose ________ is favored
sparing
in fasting, _______ and ______ levels are low and caloric deficiency decreases the production of ________
insulin and glucose
IGF-1
hypoglycemia _______ GH secretion
stimulates
famine, fasting and catabolic state all _______ plasma GH
increase
Ghrelin ________ GH release
promotes, by acute stimulatory effects on pituitary somatotrophs, influencing fuel metabolism indirectly to maintain blood glucose levels
hypoglycemia from fasting ____ GH secretion
stimulates
- effects of GH under fasting conditions are catabolic and glucose sparing
in a hypoglycemic state (fasting) what does GH do
- stimulates lipolysis
- stimulates gluconeogenesis
- inhibits glucose uptake
GH activates growth primarily via…?
Somatomedins (IGF-1)
increased growth after the fusion of epiphyseal plates, often associated with DM type II and PD/PU
acromegaly
Testosterone w/ GH in the liver ____IGH-1 secretion
enhances
Testosterone ____ release of GH from pituitary
stimulates
Effect of epinephrine in liver
decreased GH related IGF-1 secretion
what is the role of thyroid hormone in growth?
facilitates linear growth of bone byincreasing the activity of cartilage chondrocytes in the growth plate
Can growth occur without thyroid hormone, if GH is present?
no
positive effects of glucocorticoids on growth
induce GH gene expression
induce GHRH and ghrelin receptor on somatotropes
effects of excessive glucocorticoids on GH
- increase hypothalamic somatostatin (inhibits GH)
- decreases GH receptor expression in peripheral tissue
- Cushings
- exogenous glucocorts suppress growth in kids
effects of a deficiency of glucocorticoids on growth
decreased expression of GHRH and ghrelin receptors in pit
associated w/ low ACTH
