Control of Growth Hormone secretion

Question 1

What is a positive regulator of growth hormone?

Answer 1

GHRH

Question 2

What is a negative regulator of GH?

Answer 2

Somatostatin

Question 3

What is growth hormone?

Answer 3

Produced by somatotroph cells of Ant. Pit
Single chain polypeptide: ~1900aa ~22000MW
circulating half life of about 20 mins
promotes growth of bone and muscles
metabolic effects on most tissues

Question 4

Where has the growth hormone receptor been identified?

Answer 4

Liver, muscle, adipose tissue

Question 5

describe the GH receptor

Answer 5

single membrane spanning domain

Question 6

Tell me about laron syndrome:
what is it?
whats it caused by?

Answer 6

Serum GH levels higher than normal
serum IGF-1 undetectable
caused by non functioning GH receptor caused by a gene mutation

Question 7

What effect does GH have on epiphyseal cartilage growth plate?

Answer 7

increases the width causing BONE EXTENSION

Question 8

Hypopituitaryism is what?

Answer 8

this is when there is too little GH secretion in childhood, this is otherwise known as DWARFISM

Question 9

GH pituitary secreting tumour causes?

Answer 9

GH excess, in the young this causes GIGANTISM and in the adult this causes ACROMEGALY

Question 10

What are the symptoms of acromegaly?

Answer 10

Thickening of bones and soft tissues
coarsening of features
NOT height gain - growth of bones in adult no longer possible due to closure of epiphyseal cartilages at puberty

Question 11

What is the treatment of acromegaly?

Answer 11

Reduce excess GH by:
surgical removal of of GH secreting tumour
Radiotherapy to arrest tumour growth
give somatostatin analogue (reduce GH secretion)
give dopamine agonist (reduce GH secretion)

Question 12

What are the consequences of Adult GH deficiency?

Answer 12

changes in body composition - central obesity
raised lipids in blood
reduced muscle strength
bone composition - weak bones
diminished exercise capacity
cardiovascular risk
physiological well-being