hormonal control of growth

Question 1

effects of GH

Answer 1

increased protein synthesis
increased amino acid transport
increased lipolysis
reduced liver glucose uptake and increased gluconeogenesis
increased IGF production (insulin like growth factor)

Question 2

growth hormone release is

Answer 2

circadian and pulsatile

Question 3

GH release is triggered by

Answer 3

Growth hormone releasing hormone

Question 4

GH release is stopped by

Answer 4

somatostatin

Question 5

things stimulating growth hormone

Answer 5

starvation, exercise, sleep

Question 6

the starvation paradox

Answer 6

Gh helps survive prolonged starvation by switching metabolism away from proteins as a fuel source
protein sparing
makes you burn fats in preference to protein

Question 7

indirect effects of GH are mediated by

Answer 7

insulin-like growth factor

liver provides most of circulating IGF-1

Question 8

IGFs regulate

Answer 8

proliferation, differentiation and metabolism
resembles insulin structure and function
IGFs stimulate amino acid uptake and activate protein and DNNA synthesis
strongly mitogenic and hypertrophic

Question 9

2 forms of IGF

Answer 9

IGF-1 = adult form 
IGF-2 = foetal form

Question 10

GH will activate

Answer 10

IGF

Question 11

local IGF

Answer 11

is produced in heart and skeletal muscle and bone

Question 12

IGF-1 regulation

Answer 12

growth rates reflect IGF levels
IGF responds to feasting
insulin potentiates GH effects
GH cannot increase IGF levels in the absence of insulin
normal growth requires normal levels of both GH and insulin to increase IGF

Question 13

to increase IGF1 normal levels of _ are required

Answer 13

both insulin and GH

insulin potentiates GH effects

Question 14

negative feedback of GH IGF axis

Answer 14

GH gives negative feedback to hypothalamus and IGF gives negative feedback to anterior pituitary and hypothalamus

Question 15

over secretion of Gh usually due to

Answer 15

benign tumour (adenoma)

Question 16

over secretion of GH before puberty

Answer 16

this can lead to excessive growth that continues throughout childhood and puberty, leading to an extremely tall stature or gigantism

Question 17

over secretion of GH after puberty

Answer 17

this can lead to thickening of the bones of the hands, feet and jaw, causing disease known as acromegaly

Question 18

effects of acromegaly

Answer 18

cartilage enlarges, increasing the size of the nose and ears
increase in bone and cartilage often impinges on certain nerves
visual-field losses due to pressure on the optic nerves
ball’s palsy (facial paralysis on one side) due to pressure on the facial nerve
carpal tunnel syndrome: pressure on median nerve in first by excessive bone/tendon growth
spreading teeth, bite difficulties
joint and bone aches and pains
soft tissue enlarge, including the heard leading to cardiac hypertrophy
hypertension is also common

Question 19

under secretion of GH

Answer 19

under secretion of Gh before puberty causes dwarfism

after puberty, patients show few clinical symptoms

Question 20

factors that may reduce pituitary GH output

Answer 20

tumour e.g. of the hypothalamus which over secrete somatostatin
infections can affect hypothalamic GHRH of somatostatin secretion and alter GH release
GH secretion is very susceptible to irradiation e.g. after cranial radiotherapy

Question 21

GH receptor/signalling defects

Answer 21

dwarfism, pygmyism

Question 22

laron-type dwarfism

Answer 22

genetic polymorphism reducing GH receptor expression

Question 23

Baka pygmy

Answer 23

normal GH levels but reduced IGF production

Question 24

steroid hormones

Answer 24

androgens play a synergistic rose i.e. linear growth, increase muscle strength and mass, stimulating protein synthesis in many organs
testosterone and oestrogen also enhance the growth hormone release and function

Question 25

thyroid hormone

Answer 25

adequate levels of TH are required for normal growth
thyroid hormones act primary through stimulation of booth GH synthesis and secretion
TH may also increase the responsiveness of target cell to GH

Question 26

low thyroid hormones levels lead to

Answer 26

declining GH levels

stunted growth observed in thyroid deficient individuals is primary due to a deficiency in GH

Question 27

GH replacement

Answer 27

recombinant hGH developed to treat GH deficiencies in children, as well as cachexia and muscle wasting disorders

Question 28

hormones replacement therapy

Answer 28

aging - reduced lean muscle and bone mass, increase n body fat - similar to changes associated with endocrine deificency

Question 29

sport use of hormonal growth promoters

Answer 29

hGH has long been a banned substance in competition
GHRH peptides - act on the pituitary gland to stimulate the release of Gh
putative benefits - lean body mass, increase muscle mass and strength, injury resistance

Question 30

use of hormonal growth promoters

Answer 30

increase skeletal mass and lean body mass, decrease in body fat
side effects - carpel tunnel syndrome, hypertension, joint and bone aches, cancer
incidence of malignant tumours higher in patients with acromegaly
IGF signalling implicated in aging