HRR: growth hormone

Question 1

Where is growth hormone made?

Answer 1

In somatotrophs in the anterior pituitary

Question 2

What is the most important hormone required for growth?

Answer 2

Pituitary growth hormone

Question 3

What are tropic hormones?

Answer 3

Pituitary hormones

Question 4

What does GHRH do?

Answer 4

Regulate GH release via pulsatile release

Question 5

Where is GHRH made?

Answer 5

Neurons in the arcuate nucleus

Question 6

What does GHRH promote?

Answer 6

Somatotroph differentiation, GH synthesis/secretion, growth

Question 7

How does GHRH promote GH release?

Answer 7

Binds its receptor on the somatotroph and increases GH mRNA transcription and thus synthesis of GH

Question 8

What does somatostatin do?

Answer 8

It inhibits GH secretion by inhibiting GHRH arcuate neurons in the hypothalamus and blunts GH responses to GHRH at the pituitary

Question 9

Where is somatostatin made?

Answer 9

The paraventricular nucleus

Question 10

How does IGF-1 impact GH secretion?

Answer 10

It inhibits GHRH neurons and stimulates somatostatin neurons in the hypothalamus and inhibits GHRH stimulated GH release at the pituitary

Question 11

How can GH impact its own release?

Answer 11

In high levels, it feeds back to the hypothalamus and binds GH receptors on somatostatin neurons to limit GH release

Question 12

Describe ghrelin in relation to GH.

Answer 12

It is a growth hormone secretagogue, meaning its effects are similar to GHRH; they increase GH release

Question 13

What receptor does ghrelin use?

Answer 13

GHSR

Question 14

Where is most ghrelin made?

Answer 14

In the stomach! Some is made in the pituitary

Question 15

Describe the effects of ghrelin.

Answer 15

It is released during fasting and promotes food intake

Question 16

How do GH and ghrelin impact each other?

Answer 16

Their effects are additive!

Question 17

When are the greatest increases in GH?

Answer 17

At night after the onset of sleep

Question 18

What happens to pulsatility of GH as we age?

Answer 18

Frequency and amplitude of the pulsatility decrease; it peaks around puberty and declines after that

Question 19

When is a single GH blood sample useful in diagnosis?

Answer 19

Literally never. Daytime levels are normally extremely low

Question 20

What causes IGF-1 production?

Answer 20

GH engages its receptors, often at the liver, leading to signaling pathways and causing synthesis of IGF-1

Question 21

What is the major site of IGF synthesis?

Answer 21

The liver

Question 22

How does IGF-1 impact glucose uptake?

Answer 22

It increases the uptake of glucose! It can bind and stimulate insulin receptors to stimulate glucose uptake

Question 23

Compare actions of GH and IGF-1.

Answer 23

They’re really similar. Sometimes it’s hard to biologically tell which hormone did what

Question 24

How do GH and IGF impact bones?

Answer 24

Increases linear bone growth! Without it the growth plates are narrow, and cartilage production is low.

Question 25

Cells in the growth plates of bones contain what hormone receptors?

Answer 25

Androgen, estrogen, testosterone, GH, IGF-1

Question 26

How does estrogen impact bone?

Answer 26

It is protective and increases stability

Question 27

How does GH impact blood glucose?

Answer 27

Increases it; it increases gluconeogenesis in the liver and decreases glucose uptake in fat/muscle

Question 28

What does exercise do to GH?

Answer 28

Increases it

Question 29

What may be associated with GH deficiency?

Answer 29

Abnormal metabolism (lower basal metabolic rate), abnormal body composition (increased body fat), suboptimal physical performance (it is performance enhancing!!)

Question 30

What causes Gigantism?

Answer 30

Excess GH prior to puberty

Question 31

What causes dwarfism?

Answer 31

GH deficiency prior to puberty

Question 32

What might a child with GH deficiency look like?

Answer 32

Smaller stature, smaller limbs, smaller trunk, immature face, “baby fat”

Question 33

What causes acromegaly?

Answer 33

Excess GH after puberty, usually due to a pituitary tumor

Question 34

What might someone with acromegaly look like?

Answer 34

Mandibular prominence, nasal soft tissue enlargement, thickening of hands and feet, prominent forehead. It’ll alter the bone structure, which shouldn’t happen after puberty

Question 35

What does hypoglycemia do to GH?

Answer 35

Increases it

Question 36

What do amino acids do to GH?

Answer 36

Increases it

Question 37

What does puberty do to GH?

Answer 37

Increases it

Question 38

What does ghrelin do to GH?

Answer 38

Increases it

Question 39

What does somatostatin do to GH?

Answer 39

Decreases it

Question 40

What does somatomedin do to GH?

Answer 40

Decreases it