015 Normal Growth hormone axis

Question 1

Which pathway does GHRH act on ?

Answer 1

Adenylate cyclase to stimulate GH release

Question 2

Which receptor/ pathway does growth hormone act upon?

Answer 2

JAK/STAT1 pathway, which causes gene transcription of IGF and SOCS
It also activates via MAPK and PI3K

Question 3

Which chromosome is the GH gene l located on?

Answer 3

Chromosome 17

Question 4

Which gene for GH is preferentially expressed on somatotrophs of anterior pituitary?

Answer 4

GH-N

Question 5

Which gene for GH is preferentially expressed on synctotrophoblasts of placenta?

Answer 5

GH-V

Question 6

What are hypersensitivity sites?

Answer 6

Promoter regions for growth hormones
HS I and II are pituitary specific
HS IV are placenta pspecific
IS III and V found both placenta and pituitary but nowhere else.

Question 7

Which IGF acts on insulin like receptors?

Answer 7

IGF1 (IGF2 controls growth of foetus)

Question 8

How do GH and IGF work together in connective tissue?

Answer 8

GH activates differentiation of chondrocytes and fat

IGF1 mediates clonal expansion of these cells.

Question 9

How do GH and IGF work in long bones?

Answer 9

They both stimulate growth plate thickness –> fibroblast differentiation into chondroblasts and osteoblast at growth plate of long bones.