Normal growth & clinical aspects Flashcards
(25 cards)
does insulin stimulate or inhibit growth?
stimulates growth
what is the functions of growth hormone and is this direct and indirect effects?
growth and development (indirect) regulates metabolism (direct)
what is required to allow GH to stimulate growth?
thyroid hormones & insulin
in adulthood when we stop growing, what is GH required for?
GH is required for maintenance and repair of tissues
what is responsible for the indirect action of GH on growth?
somatomedian C
IGF-1
where is IGF-1 secreted from and what promotes its release?
GH stimulates IGF-1 release from the liver
how does IGF-1 provide a negative feedback loop to GH?
IGF-1 inhibits the release of GHRH and stimulates GHIH
can also have an effect on the release of GH from the anterior pituitary
during puberty when there is massive spikes in GH production, what provides a buffering mechanism so that adolescences don’t grow in dramatic bursts?
50% of GH is bound to carrier proteins which helps to smooth out the erratic pattern of secretion
also provides a reservoir of GH in the blood when required
the closure of the epiphyseal plates after puberty is due to what hormone?
sex hormones
what is responsible for the production of cartilage in bone growth?
GH stimulates the differentiation of chondrocyte precursors to form chondrocytes.
these cells then begin to secret IGF-1 which they then respond to
IGF-1 lays down the cartilage which is the foundation for bone growth
how does GH have a direct effect on metabolism?
GH increases gluconeogenesis in the liver to increase glucose
it also reduces the ability of insulin to stimulate glucose uptake by muscle and adipose tissue
this causes hyperglycaemia making glucose readily available to cells needing it for growth
in patients who have an increase in GH release, how might they present with diabetogenic signs?
GH increases blood glucose in order to mobilise energy stores to make it readily available for cells who require glucose for growth
what effect does GH have on muscle, liver and adipose tissue?
GH decreases insulin’s ability to stimulate glucose uptake by muscle, liver and adipose tissue
however GH increases the amino acid uptake and protein synthesis
because GH inhibits the actions of insulin, how does it increase the uptake of glucose by other cells who require it for growth?
GH inhibits insulin to increase blood glucose to make it readily available for tissues who require it for growth
but liver, muscle and adipose tissue are the only tissues that are insulin sensitive
therefore other cells are able to uptake the glucose without insulin
when is release of GHRH at it highest and why?
during deep delta sleep because this is when we have our lowest energy requirements
what provides the buffering qualities to GH release during sleep and how?
IGF-1
levels remain constant during sleep despite the dramatic fluctuations of GH
what are stimuli that increase GHIH?
glucose
FFA
REM sleep
cortisol
what stimuli increase GHRH?
decrease in energy supply to cells increased AA in plasma stressful stimuli e.g. infection delta sleep oestrogen and testosterone
why does an increase of AA stimulate GHRH but an increase in glucose stimulates GHIH?
GH promotes AA uptake and protein uptake by muscle and liver
whereas GH promotes an increase in blood glucose by reducing the ability of insulin to stimulate glucose uptake
for growth and development, IGF-1 promotes the uptake of glucose into what type of tissue?
muscle
what is cretinism?
a condition where a child is hypothyroid from birth
why does hypothyroidism from both cause stunted growth?
thyroid hormone is permissive to the actions of GH
therefore with no TH the GH won’t be stimulated despite normal levels
what is the cause of gigantism and acromegaly ?
gigantism is caused by an over secretion of GH before the epiphyseal plate closes
Acromegaly is over production after it closes
how would you treat gigantism or acromegaly?
resection of pituitary tumour
somatostatin analogues
