Week 7 Endocrinology Growth Hormone Flashcards
Which of the following enhance GHRH and which surpress it?
- obesity
- insulin
- estradiol
- starvation
- somatostatin
- glucose
- ↑age
- ghrelin
- glucocorticoids
Enhanced by: estradiol, ghrelin, glucocorticoids (acutely) and
starvation
Blunted by: somatostatin, obesity, insulin, glucose, ↑age
WHat is the effect of grehlin on GH?
Increases GHRH release.
- Natural ligand of the growth hormone
secretagogue receptor (GHS-R) →
increases GHRH release - Enhances GH secretion
- Maintains blood glucose levels during starvation (via GH)
What is the effect of somatostatin on growth hormone?
Surpresses GH
Suppressive effect on multiple pituitary hormones (including GH and TSH) and insulin
Somatostatin analogues are used in the treatment of GH excess and other
neuroendocrine conditions
Where are most of the growth hormone receptors located and what is their main function?
- GHR mostly expressed in liver
- Predominant action is stimulation of hepatic IGF-1 (insulin like growth factor) synthesis and secretion
What is the main function of insulin like growth factor? (IGF-1)
Responsible for most of the linear growth-promoting
activities of GH
40% of IGF-1 variation is heritable and relates to final
height.
- Decrease blood glucose / improve insulin
sensitivity - Stimulate whole body protein synthesis and
inhibit proteolysis - Reversal of catabolic effects of
glucocorticoids on protein synthesis - Anabolic effect on bone (↑ markers of bone
formation)
5 main functions of GH
- Acts directly and indirectly (via IGF-1) to stimulate linear growth -
action on epiphyseal growth plates - Increases lipolysis and lipid oxidation (mobilization of stored TG)
- Stimulates protein synthesis
- Antagonism of insulin action
- Phosphate, water and sodium retention
What is the negative feedback loop for GH?
IGF-1 decreases GH release
What is Laron syndrome?
GHR mutations
Result is high GNRH and GH but low IGF-1
- Severe postnatal growth failure (short limbs)
- Small head circumference, saddle nose,
prominent forehead, delayed skeletal
maturation, osteopenia and obesity
What should do if there is GH deficiency in children?
Give GH while epithysis open
GH replacement therepy in adults?
In mild cases of GH defienciency it is not reccomended to give GH replacement therepy as growth isn’t an issue it is more effects of body comosition and the side effectscan be quite strong.
Can give in extreme cases
What is Acromegaly
excessive growth hormone
How does acromegaly present?
Enlarged skull, nose, lips, jaw, feet, myopathy, carpel tunnel syndrome (as increased bond and soft tissue causes nerve compression)
What is the common cause of acromegaly?
Somatotroph macroadenoma
As macro can present with visual effects
Goliath probs had a pituitary macroadenoma hence the one eye
What is the name for too much growth hormone
Acromegaly
What is somatostatin?
Somatostatin (Growth Hormone-Inhibiting Hormone) suppresses GH release.
