Growth Hormone (9)

Question 1

What type of hormone is GH?

Answer 1

Peptide hormone

Question 2

Where is GH produced?

Answer 2

Anterior Pituitary

Question 3

What two regulation factors does the hypothalamus produce? What are their effects?

Answer 3

GHRH: stimulates

Somatostatin: Inhibitory

Question 4

What factor does the stomach and pancreas secrete that regulates GH?

Answer 4

Ghrelin

Question 5

What does the integration of GHRH and somatostatin result in?

Answer 5

Episodic, pulsatile secretion

Question 6

What are the effects of GHRH (name 4)?

Answer 6

1- increased GH gene transcription

2- Promotes GH release

3- Stimulates production of GHRH receptor

4- Stimulates somatostain release

Question 7

What are the effects of Somatostain (name 4)?

Answer 7

1- Decreasespulse frequency

2- Decreases pulse amplitude

3- No impact on GH synthesis

4- Inhibits GHRH release

Question 8

When do growth hormone pulses mainly occur?

Answer 8

At night at higher frequencies

Question 9

What do the following factors allow for?

Deep sleep, exercise, sex steroids, hypoglycemia, amino acids, stress, dopamine agonists

Answer 9

Stimulate GH secretion

Question 10

What do the following factors allow for?

IGF- I, Obesity, glucocorticoids, hyperglycemia, free fatty acids, GH, beta- adrenergic agonists

Answer 10

Inhibition of GH secretion

Question 11

What doe increased levels of GH and IGF-I do to somatostatin release?

Answer 11

Increase somatostatin release

Question 12

What doe increased levels of GH and IGF-I do to GHRH release?

Answer 12

decrease GHRH release

Question 13

What type or receptor does GHRH bind to?

Answer 13

Gs protein coupled receptor on somatotrophs

Question 14

When GHRH binds its receptor, what are the effects within the cell?

Answer 14

1- increased cAMP which activates PKA to Phosphorylate CREB…which then augments Pit-1 a transcrption factor that upregulates GH and the GHRH receptor

2- increased Ca++ which leads to secretion of GH

Question 15

What type of receptor is the GH receptor?

Answer 15

Transmembrane receptor of the cytokine family

Question 16

Where are the major sites of action of GH receptors?

Answer 16

Bone, Liver, Adipocyte, Muscle

Question 17

What pathway do receptors for GH activate?

Answer 17

JAK/ STAT pathway of signal transduction

Question 18

Do GH receptors have inherent tyrosine kinase activity?

Answer 18

No

Question 19

What does the binding of GH to its receptor cause?

Answer 19

receptor dimerization and binding of a JAK tyrosine kinase

Question 20

What do activate JAKS do?

Answer 20

Phosphorylate the STATs, which as dimers translocate to the nucleus and act as trascription activators

Question 21

What are the effects of GH on the liver?

Answer 21

production of IGF-I and stimulateshepatic glucose production

Question 22

What are the effects of GH on the adipocytes?

Answer 22

Stimulates the release and oxidation of free FAs by the reduction of the activity of Lipoprotein lipase

Lipogenesis is reduced

Question 23

What are the effects of GH on skeletal muscle?

Answer 23

anabolic actions on skeletal muscles…stimulates amino acid uptake and incorporation into proteins and suppresses protein degradation

Question 24

What are the effects of GH on the brain?

Answer 24

Affects mood and behavior

Question 25

What are the effects of GH on bone?

Answer 25

differentiation of prechondrocytes into chondrocytes

Question 26

True or False: GH induces growth in animals that lack insulin

Answer 26

false

Question 27

What is primarily sued for screening when considering GH deficiencies?

Answer 27

IGF-I (because levels are more stable and not cyclic)

Question 28

How do Insulin, IGF-I and IGF-II resemble one another?

Answer 28

all have A, B and C domains which share a high degree of AA sequence homology

Question 29

What additional piece do IGF-I and IGF-II have when compared to insulin?

Answer 29

D domain

Question 30

What happens when the IGF-I recepter dimerizes?

Answer 30

Autophosphorylation of the receptor recruits IRS-1 and Shc

Question 31

What happens when IRS-1 and Shc are phosphorylated by the IGF-I receptor?

Answer 31

they recruit other proteins to the membrane which then activates the PI3-inase and Ras/MAP kinase pathways. Both of these pathways regulate cellular transcription

Question 32

What plays a large role in the growth spurt during puberty?

Answer 32

sex hormones

Question 33

What is the cause of Laron Syndrome?

Answer 33

Point mutation or deletion in IGF receptor that causes low IGF-I concentrations and normal/ elevated GH concentrations

Question 34

What is Laron syndrome treated with ?

Answer 34

rhIGF-1

Question 35

What can gigantish lead to?

Answer 35

hyperglycemia ----> diabetes mellitus due to degradation of beta cells in the pancreas

Question 36

What causes acromegaly

Answer 36

Growth hormone secreting adenomas

Question 37

What are the anatomical characteristics of Acromegaly?

Answer 37

protrusion of the jaw, enlarged tongue, enlarged hands and feet, carpal tunnel syndrome, reduced strength

Question 38

What are the implications of GH deficiencies for cardiovascular disease?

Answer 38

Increases visceral adipose tissue and decreased myocardial function

Question 39

What happens to GH as a person ages?

Answer 39

Levels decrease and this contributes to some normal effects of aging...like loss of muscle mass and increased interstitial body fat

Question 40

What is GH approved to treat?

Answer 40

``` Gh deficiency Idiopathic short stature Turner syndrome Prader-Willi syndrome Chronic renal insufficiency Small for gestational age ```

Question 41

If you have celiac disease, how is your IGF-I level affected?

Answer 41

Reduced levels because if nutritional deficiencies related to the disease

Question 42

What is the short stature in Turner syndrome attributed to?

Answer 42

Haplonoinsufficiency of the SHOX gene because of an absence of an X chromosome

Question 43

What are the most common genetic syndromes that cause short statures in the US?

Answer 43

Turn and Down sundrome

Question 44

How is the SHOX protein regulated?

Answer 44

It is developmentally regulated. It is expressed throught the fetak growth plate but is most concentrated in the hypertrophic zone during childhood