Growth hormone

Question 1

Mechanism of action of GH through activation of………………….

Answer 1

tyrosine kinase

Question 2

describe the growth promoting effect of GH

Answer 2

1.increasing number of cells through
++cell division—apoptosis
2.increasing size of cells through protein anabolic effect and retention of all element required for growth

Question 3

what is the effect of GH on bone

Answer 3

1.increasing reproduction of chondrocyte and osteogenic cells
2.increase deposition of peotein by these cells
*increasing bone length is done through formation of new cartilage at the epiphyseal plate then converted to bone –elongation of shaft
*increasing bone thickness is done through formation of new bone on the surface of old bone by osteoblast

Question 4

what are somatomedins

Answer 4

☺ Polypeptides
☺ Secreted by the liver & other tissues in response to their
stimulation by GH.
☺ increased by GH & decreased by protein deficiency.
☺ Structurally similar to insulin

Question 5

what are actions of somatomedins

Answer 5

1- Protein synthesis
2- Chondrogenesis.
3- Growth
4- Weak insulin-like action.
5- Inhibit lipolysis.

Question 6

GH has NO effect on:1…………..
2…………

Answer 6

1- Growth of nervous tissues.
2- Tissue cell maturation

Question 7

function of IGF-II is ………………

Answer 7

intrauterine growth of fetal tissues

Question 8

what is the effect of GH on carbohydrate metabolism

Answer 8

diabetogenic effect
GH produces:
increasing → hepatic output of glucose (gluconeogenesis)
 antiinsulin effect on muscles → decreasing glucose uptake.
This leads to:
 Hyperglycemia
 Compensatory increasing in insulin secretion.
 Insulin resistance.

Question 9

effect of GH on Fat metabolism

Answer 9

GH produces:
 activation of lipase → IN plasma FFA level →IN energy
 ketosis &
fatty liver
ketogenic &lipolytic

Question 10

effect of GH on protein metabolism

Answer 10

It enhances almost all facets of amino acid uptake and protein synthesis by cells,
while at the same time reducing the breakdown of proteins.

Question 11

how the GH secretion is regulated

Answer 11

1- Hypothalamic control:
GH secretion is regulated by:
☺ GHRH
☺ GHIH (somatostatin)
Ghrelin which its main site of synthesis and secretion is the stomach but also produced
in the hypothalamus has marked growth hormone-stimulating activity.
2- Feedback control:
increaseGH→:
♫ IGF1→ – of GH secretion & ++ GHIH secretion.
3- Diurnal (circadian):
GH  after the onset of deep sleep (non-REM).
4.other factors