endocrinology 3 Flashcards
What are the 2 forms of GH signalling for AP?
TROPHIC OR DIRECT
What are the 2 types of growth?
bone growth (height)
soft tissue (weight)
Where is the site of bone growth?
epiphyseal plate
What type of bone growth is bone lengthening?
endochondral
What is endochondral ossification?
cartilage (hyaline) is replaced by bone
chondrocytes lay down cartilage and osteoblast replace this with bone
When does the epiphyseal growth plate close?
adolescence
What are the 2 types of growth hormone control GH release form AP?
GHRH (release)
GHIH (inhibitory)
What factors can influence GF release from hypothalamus?
circadian rhythm
stress
cortisol fasting
When growth hormone is release form the AP, where does it target?
liver and other tissues
When GF influences the liver and other tissue, what does this lead to the release of?
insulin-like GF
IGF
In the last stage in the GF cascade, what does IGF influence?
cartilage growth
increase blood glucose
bone and tissue growth
What can be a bad effect of the excessive GH?
increase blood glucose and be pro-diabetic
Why is GH atypical for a peptide hormone?
has a plasma binding protein (like steroids)
What is the benefit of GH having a plasma binding protein?
extend half life
What are the direct effects of GH?
growth and metabolism
What are the trophic effects of GH?
Effects on growth and metabolism through stimulation of insulin-like GF-1 (IGF-1)
Where is IGF-1 released from?
liver and other cells
What is the release pattern of GH?
CYCLIC
i.e. at night, the energy is diverted to growth/development
When to conc of GH peak and decline?
peak = early childhood/adolescence
decline = later life
What does GH stimulate in bone?
differentiation of precursor cells in bone
pre-chondrocytes to chondrocytes
effectively… GH stimulates cell maturation and IGF-1 production
then IGF-1 stimulates cell division and tissue growth
What do chondrocytes produce?
IGF-1
What does IGF-1 stimulate in bone?
Apart from bone, what is the effect of GH and IGF-1 in muscles and other tissues?
stimulate protein synthesis
What receptors does IGF1 act upon, because it is similar to another molecule?
insulin receptors
insulin and IGF can and each others receptors - lots of cross over
What do IGFs behave as?
auto/paracrine (local) and a hormone (endocrine)
What molecule stimulates chondrocytes to divide and produce cartilage?
IGF-1
What are the metabolic effects of GH?
uptake plasma amino acids (for protein synthesis)
breakdown of fat (energy for growth)
spares glucose stores (responsible hormone)
What does GH preferentially gain energy from?
fat stores as apposed to glucose stores
this is called a responsile hormone
What are the metabolic effects of IGF-1 (and insulin)?
uptake of plasma amino acids (for protein synthesis)
glucose/energy substrate uptake into cells
How is glucose stored in cells (for growth)? (promoted by IGF-1)
glycogen
What hormones allow tight regulation of energy stores?
GH
IGF-1
