Regulation of Growth

Question 1

What does growth depend on?

Answer 1

genetic determination
an adequate diet
freedom from chronic disease and stress
normal levels of growth influencing hormones

Question 2

What are the hormones regulating growth?

Answer 2

TH - hypothyroid children stunted
Insulin - deficiency blocks growth, hyper spurs growth
Testosterone - pubertal growth spurt, depends on presence of GH
Estrogens
GH
IGF-1
Calcitonin, PTH and Vit D

Question 3

What are the growth stages ?

Answer 3

prenatal
growth in infancy
adolescence

Question 4

What regulates prenatal growth?

Answer 4

maternal factors, fetal insulin and IGF

Question 5

What regulates growth in infancy?

Answer 5

genetic factors, GH production, TH, IGF

Question 6

What regulates growth in adolescence?

Answer 6

GH, Insulin, IGF and sex hormone surge

Question 7

How much GH is circulating a day?

Answer 7

500microg

Question 8

What is the half life of GH?

Answer 8

25-30mins

Question 9

What is GH also known as?

Answer 9

somatotropin

Question 10

How is growth hormone regulated in the hypothalamus?

Answer 10

GHRH and GHIH

Question 11

What does GH stimulate in the liver?

Answer 11

IGF

Question 12

What is the signalling pathway which results in GH release?

Answer 12

GHRH binds the receptor -> Gas -> cAMP -> PKA -> CREB -> synthesis of Pit-1 mRNA -> Pit-1 TF -> synthesis of GH mRNA -> GH synthesis and release

Question 13

What is the signalling pathway which releases IGF -1 ?

Answer 13

GH - binds 2 receptors -> JAK tyrosine kinase -> STAT transcription factor -> gene expression of IGF-1

Question 14

What are the direct effects of GH?

Answer 14

stimulates growth - hypertrophy - increases size and volume of cells - bone thickness
stimulates cell reproduction - hyperplasia - increase no. of cells - bone length

Question 15

What is the effect of GH on metabolism?

Answer 15

stimulates cell metabolism
increases protein synthesis
increases fat breakdown for energy
carbohydrate metabolism changes

Question 16

How does GH affect carbohydrate metabolism?

Answer 16

decreased use of glucose for energy
increased glycogen deposition
increased blood glucose levels
increase insulin secretion

Question 17

what are the negative feedback mechanisms for GH?

Answer 17

high levels of IGF-1 stimulates GHIH

high levels of GH inhibits GHRH

Question 18

what are the negative feedback mechanisms for GH?

Answer 18

high levels of IGF-1 stimulates GHIH

high levels of GH inhibits GHRH

Question 19

When is GH released at most?

Answer 19

pulsatile release, most during sleep

Question 20

What stimulates GH secretion?

Answer 20

exercise, stress, fasting, amino acids

Question 21

What inhibits GH secretion?

Answer 21

high glucose

Question 22

What responses does IGF-1 stimulate?

Answer 22

linear bone growth and cell proliferation leading to soft tissue growth

Question 23

What do IGFBPs do?

Answer 23

bind circulating IGF with high affinity and specificity

Question 24

What are the functions of IGFBPs?

Answer 24

act as carriers of IGF in the plasma
prolong the half life of IGF in circulation
regulate IGF access to receptors in ECF

Question 25

What is the most abundant form of IGFBP?

Answer 25

IGFBP 3

Question 26

What are the functions associated with IGFBP 3 and IGFBP 1?

Answer 26

IGFBP3 stimulates growth stimulation

IGFBP 1 inhibits growth