Growth Hormone Flashcards
Where is growth hormone produced?
Anterior pituitary
What stimulates growth hormone production?
GHRH - growth hormone releasing hormone
What inhibits growth hormone production?
Somatostatin
How are the effects of GH exerted?
Indirectly via IGFs (insulin-like growth factors)
What are the effects of GH in children?
Stimulates long bone growth
Stimulate cartilage growth
What are the effects of GH in adults?
Maintain muscle and bone mass
Promote healing and tissue repair
Modulate metabolism
What increases GH release?
Stress Exercise Decrease in glucose/fatty acids Fasting Deep sleep
What decreases GH release?
REM sleep
Increase in glucose/fatty acids
Obesity
How is GH secretion regulated?
Long loop negative feedback
- mediated by IGFs
- inhibit release of GHRH + GH
- stimulate release of somatostatin
Short loop negative feedback
- mediated by GH
- stimulation of somatostatin release
What happens with GH deficiency?
Pituitary dwarfism
- proportionate dwarfism
- responds to GH therapy
- height below 3rd percentile
- delayed sexual development in teens
What happens with GH excess?
In childhood
- gigantism
- often caused by pituitary adenoma
In adults
- acromegaly
How does GH exert its effects on cells?
GH receptors activate janus kinases
Janus kinases activate signalling pathways
Transcription factor activation + IGF production
What are IGFs?
IGF 1 - growth factor in adults
IGF 2 - involved in fetal growth
Modulate
- hypertrophy
- hyperplasia
- increase rate of protein synthesis
- increase rate of lipolysis
