L6 growth hormone

Question 1

explain the structure of GH

Answer 1

is a protein 191aa, similar structure to prolactin nd placental lactogen.
structural variation means that GH of different species may not work on other species

Question 2

Growth hormone is secreted from

Answer 2

adenohypophysis

Question 3

what controls growth hormone secretion?

Answer 3

GH-releaseing hormone (GHRH or somatocrinin), ghrelin, and GH release- inhibiting hormone (GHIH or somatostatin), and negative feedback from GH, and IGF-1 (Part B).

Question 4

explain the structure of GH

Answer 4

is a protein 191aa, similar structure to prolactin nd placental lactogen.
structural variation means that GH of different species may not work on other species

Question 5

General physiological effects of Growth hormone

Answer 5

promote growth in developing, well-fed animals and provide a ready source of energy during starvation

indirect anabolic actions= mediated by polypeptides known as somatomedins (IGF-1) =

anti-insulin/catabolic actions during starvation result from the absence of IGF-1 = releasing energy forth cells into the blood as the body is starving

Question 6

somatotropin

Answer 6

another name for growth hormone

Question 7

somatomedins

Answer 7

named because they mediate the activity of somatotrophin

Question 8

explain the typical release of GH

Answer 8

1/2 during deep sleep

Question 8

explain the typical release of GH

Answer 8

GH release is stimulated by deep (nonREM) [complete relaxation] sleep, but is inhibited during REM sleep.
GH release is also stimulated by stress (sympathetic response) and exercise (high resistance training or training that is high intensity above lactate threshold for 10 mins) - -> exercise for seniors
GH release is inhibited by elevated glucose, and stimulated by low glucose and high levels of certain amino acids (arginine).
Implications for wt loss (circ rhythm and food deprivation).

Question 9

explain why is GH levels go up and down`

Answer 9

The episodic pattern of GH release is important in modulating its metabolic activities, because the nearly complete absence of GH effects during trough periods is vital in maintaining its anabolic versus catabolic actions on target tissues. The plasma half-life of GH is about 20 min., whereas that of IGF-1 is much longer.

Question 10

Factors known to stimulate GHRH and therefore GH secretio

Answer 10

the hormones ghrelin, progesterone (in dogs), glucagon, thyroxine, ACTH-releasing hormone (CRH), and thyrotropin-releasing hormone (TRH; in nonmammals), as well as stress, exercise, lactation, sleep rhythms, and certain amino acids (e.g., Arg).

Question 11

Factors associated with a decrease in GH output

Answer 11

nclude 􏰁- adrenergics, hyperglycemia, glucocorticoids, synthetic progestins (in primates), and GH and IGF-1 negative feedback (Part B).

Question 12

explain relation between IGF-1 and GH and insulin in young animals

Answer 12

Secretion of IGF-1 (also known as somatomedin C) from the liver and other tissues of young animals, is increased by good nutrition, GH, and insulin (Part E)

Question 13

During starvation GH, IGF-1 and insulin levels

Answer 13

GH rises
IGF-1 and insulin decrease

Question 14

explain cartilage growth with GH and IGF-1

Answer 14

For example, GH may act on cartilage to convert stem cells into cells that respond to IGF-1, allowing locally produced and circulating IGF-1 to make cartilage grow.

Question 15

explain the relation between T3 and T4 with GH

Answer 15

All of these anabolic actions are enhanced by the concurrent presence of thyroid hormones (T4 and T3).

Question 16

explain the anti-insulin actions of GH

Answer 16

manifested primarily through carbohydrate and lipid metabolism, and interference with insulin’s action on the liver, muscle and adipose tissue.

interferes with insulin

stimulates - hepatic gluconeogenesis and adipose tissue lipolysis
decreasing - carbohydrate utilisation by muscle and adipose tissue
also spares breakdown of muscle protein (cortisol does not)

Question 17

List GH direct actins via GH to a receptor for muscle

Answer 17

stimulates AA uptake
decrease glucose uptake ( increases blood glucose)
Inhibits protein break down

overall increases muscle mass

Question 18

GH action when directly interacting with receptor of adipose tissue

Answer 18

decreases glucose uptake = increases blood glucose
increase fat breakdown (lipolysis)

overall = Decrease in fat deposits

Question 19

GH actions direct via GH-R

Answer 19

increase protein synthesis
increase gluconeogenesis
stimulates IGF production

overall increasing blood glucose (anti insulin effect)

Question 20

GH actions mediated by IGF-1s

Answer 20

acts on growth plate chondrocyte to increase protein and collagen synthesis and cell hypertrophy

Overall - increase linear growth

Question 21

IGF-2 works with GH to do what?

Answer 21

IGF-2 - tissue and organ growth, IGF-2 acts on numerous tissues to increase protein, RNA and DNA synthesis

Question 22

Explain IGF-1 levels through life via graph

Answer 22

Question 23

explain GH and IGF-1 impact on long bones once growth plates close

Answer 23

they can no longer impact the growth of the bone

Question 24

explain GH action on animals lung and mature

Answer 24

Growing animal (open epiphysis):
GH causes true growth but also metabolic effects:
Increase blood glucose (anti-insulin effect)
Stimulate lipolysis (anti-insulin effect)
Stimulate protein synthesis, decrease protein catabolism

Mature/adult animal (closed epiphysis)
Maintains muscle mass
Metabolic functions as above

Question 25

regulation of GH what inhibits it and what releases it

Answer 25

SST = somatostatin = GH Inhibiting Hormone
GHRH = GH Releasing Hormone

Question 26

list the factors that stimulate growth hormone

Answer 26

Decreased blood glucose
decreased blood fatty acids
starvation of fasting, protein deficiency
trauma, stress, excitement
exercise
testosterone, estrogen
deep sleep (not REM sleep)
Growth hormone releasing hormone and Ghrelin

Question 27

Inhibit Growth hormone secretion

Answer 27

Increased blood glucose
increased blood free fatty acids
Aging
obesity
Somatostatin ( gH - inhibitory hormone)
growth hormone exogenous ( as it is a negative feedback)
Somatomedins ( insulin-like growth factor)

Question 28

Transport of GH in the blood

Answer 28

about 50% of GH is bound to Growth hormone-Binding Protein (GHBP)

GHBP increases the half life of GH but when it is bound it is not biologically available

The GHBP is identical to the ligand binding domain of the GH receptor, and may be derived from alternative splicing of the GH receptor RNA.

Question 29

Roles of IGF Binding hormone proteins

Answer 29

IGFs bind several ( at least ten different IGF binding proteins (IGFBPs)

Several possible actions of IGFBPs have been proposed.
Some IGFBPs are believed to inhibit the action of IGFs by binding them and making them less biologically available:

Question 30

roles of IGF binding proteins (2) that are proposed and significance of regulating these

Answer 30

some - enhance IGF action ( possible delivering to site or increasing half life = increase stimulation)

IGF may act independently of IGFs, as some have been observed on cell membranes

Thus, regulating the expression of IGFBPs influences IGF activity

Question 31

Explain IGFBP proteases and there significance

Answer 31

these degrade IGFBPs, thats how they regulate them

thus by regulating IGFBPs, its means that you are regulating IGFs

Specific proteases have been identified for most IGFBPs.

Question 32

GH deficiency

Answer 32

Hyposecretion in adult = no major symptoms
Hyposecretion in young = pituitary dwarfism
Short stature
Normal body proportions
Poor muscle development, excess subcutaneous fat
If diagnosed before puberty, replacement therapy gives near normal growth