growth hormone

Question 1

where is the growth hormone produced

Answer 1

anterior pituitary

Question 2

which anterior pituitary cell type produces growth hormone

Answer 2

somatotroph

Question 3

growth hormone circulates freely or bound?

Answer 3

bound to GH-binding protein

Question 4

describe the function of GHRH and somatostatin (hormones produces by hypothalamus)

Answer 4

• GHRH: acts on somatotrophs to induce synthesis and release of GH
  
  • Gs mediated
• somatostatin: acts on somatotrophs to inhibit GH secretion
  
  • Gi mediated

Question 5

How do GHRH and somatostatin reach the anterior pituitary?

Answer 5

reaches the somatotrophs in the anterior pituitary through the portal veins

Question 6

what is the direct effect of growth hormone? Indirect effect?

Answer 6

• direct effect: maintaining plasma glucose
• Indirect effect: growth

Question 7

glycogen synthesis

Answer 7

conversion of glucose to glycogen, the storage form of glucose

Question 8

oxidation

Answer 8

using something for fuel, e.g. converting glucose to ATP

Question 9

glycogenolysis

Answer 9

breakdown of stored glycogen to yield glucose

Question 10

gluconeogenesis

Answer 10

synthesis of new glucose, conversion of amino acids to glucose

Question 11

how does GH effect metabolism

Answer 11

• increase lipolysis in adipose tissue
• increase gluconeogenesis in liver
• increase amino acid uptake and protein synthesis in muscle

Question 12

growth hormone is a protein anabolic hormone. what does this mean

Answer 12

stimulate protein synthesis, muscle growth, and insulin.

Question 13

describe how GH has a glucose sparing effect

Answer 13

• decreases glucose uptake and use by muscle, liver and adipocytes
• increases liver glucose output by gluconeogenesis
• net effect = increase in glucose

Question 14

GH is a lipolytic hormone. Describe this

Answer 14

• activates triglyceride breakdown and increases free fatty acid release in adipose tissue

Question 15

the indirect effects of GH are carried out by what

Answer 15

• growth caried out by liver generated insulin-like growth factors (IGF-1)
  
  • structurally related to proinsulin

Question 16

what is Insulin-like growth factor (IGF) actions on growth

Answer 16

• increase in linaer bone growth
• action on growth plates of long bones
  
  • increase amino acid uptake and protein and collagen synthesis -> promotes hyperplasia and hypertrophy of organs

Question 17

The pubertal peak rate of growth corresponds to the peak serum concentrations of

Answer 17

IGF-1

Question 18

release of GH follows what type of rhythm

Answer 18

• diurnal (sleep-wake) rhythm
  
  • GH levels remain low during day
  • with sleep: sharp rise at onset, then steady drop throughout sleep time (70% of total secretion)
    
    • due to pulsatile release of GHRH

Question 19

how is GH regulated via IGF

Answer 19

• IGF acts on the hypothalamus to stimulate somatostatin release and inhibit GHRH release -> inhibits GH release from anterior pituitary
• IGF has a negative feedback loop with anterior pituitary

Question 20

how is GHRH regulated

Answer 20

GHRH inhibits its own release at the hypothalamus

Question 21

how is growth hormone regulated

Answer 21

• inhibits its own secretion from the anterior pituitary
• may also stimulate somatostatin release at the hypothalamus