Somatotropic Axis

Question 1

GH

Answer 1

• protein; t1/2 6-20 min
• most abundant APH (10x more)

Question 2

Somatomedins

Answer 2

• several classes; IGF-1 to 7
• polypeptides w/ 40% homology to insulin

Question 3

IGF-1

Answer 3

• systemic and autocrine effects
• low neonatally, high at puberty, lower later in life
• needed for skeletal & extra-skeletal development, adipocyte differentiation

Question 4

IGF-2

Answer 4

• prominent during embryonic/fetal growth w/ insulin

Question 5

The largest GH peak is about ________ after the onset of sleep

Answer 5

1 hr

Question 6

_______ coded by the same gene as the GH-R

Answer 6

GHBP

Question 7

GH secretion occurs as several large ________ or _______ each day, ___ to ____ in duration

Answer 7

Pulses; peaks; 10; 30

Question 8

_________ is almost entirely bound to transport proteins

Answer 8

IGF-1

Question 9

In older animals, GH and IGF’s remain essential regulators of ________________ and ______________

Answer 9

Tissue renewal; metabolism

Question 10

Some IGF-1 transport/binding proteins have an ____________ function

Answer 10

Endocrine

Question 11

________ and _______ act on the growth plate of long bones in children/young animals

Answer 11

GH; IGF-2

Question 12

_____ promotes the growth of cartilage while _______ promotes the ossification (calcification) cartilage cells

Answer 12

GH; IGF-2

Question 13

______ stimulates the synthesis and release of IGF-1 in many tissues, not just the liver

Answer 13

GH

*very difficult to differentiate b/w direct actions of GH and those of IGF-1
*both appear to exert opposite actions in some tissues — suggests that they do have independent roles!

Question 14

Other physiological roles of GH

Answer 14

• Contributes to the maintenance and function of pancreatic islets
• Stimulates the immune system
• Anti-aging effects
• Stimulates the growth and regeneration of internal organs except for the brain
• Normal reproduction

Question 15

GH can cross-react with ______

Answer 15

Prl-R

Question 16

Commercial Applications of GH

Answer 16

• Increasing milk production, leaner cows
• Generation of transgenic salmon GH gene (overexpressed)

Question 17

Problems with GH use

Answer 17

• increased animal stress (high milk production. & mastitis)
• adverse effects on reproduction (cystic ovaries, uterine disorders, decreased birth weight)

Question 18

Gigantism

Answer 18

• Hypersecretion of GH before puberty
• GH influences IGF release from the liver and therefore stimulates extensive bone growth
• Usually caused by a tumor on the anterior pituitary gland

Question 19

Acromegaly

Answer 19

• Most commonly affects “middle aged” individuals
• Hypersecretion of growth hormone after epiphyseal plate closure
• Can result in severe disfigurement
• In over 90% of acromegaly patients, the overproduction of GH is caused by a benign tumor of the pituitary gland (pituitary adenoma)

Question 20

Dwarfism

Answer 20

• If GH is lacking, stunted or even halted growth may become apparent
• Children may grow slowly and puberty may be delayed by several years or indefinitely
• Dwarfism has no single definite cause:
  • Mutations of specific genes
  • Damage to the pituitary gland
  • Turner’s syndrome
  • Malnutrition
  • Stress (psychogenic/psychosocial dwarfism - PSS)