Pituitary Physiology & Pharmacology- Teresa

Question 1

What are the hormones in the growth hormone axis?

Answer 1

Hypothalamus: GHRH and somatostatin (GHIH), also dopamine which is inhibitory
Pituitary: GH

Question 2

What type of receptor is the GHRH receptor?

Answer 2

GPCR- Gas

Question 3

How does somatostatin work?

Answer 3

Via SSTR-1 through -5 which are G-inhibitory GPCRs

Question 4

Where is GH made ?

Answer 4

Anterior pituitary- somatotrophs (acidophils)

Question 5

What is GH bound to in the serum?

Answer 5

GH binding protein (GHBP)

Level of GHBP indicates tissue levels of GH receptor since it is the ectodomain of GH receptor

Question 6

What is the GH receptor on target cells?

Answer 6

Transmembrane, cytokine receptor that activates JAK/STAT pathway

Question 7

What does liver produce in response to GH?

Answer 7

IGF-1 (somatomedin)

Question 8

What are the actions of GH?

Answer 8

1. Protein Metabolism- increase aa uptake and protein synthesis
2. Mineral Metabolism- increase mineral density in bones
3. Carbohydrate Metabolism- decrease carb utiliztion–>hyerglycemia d/t reduced uptake of glucose and increase liver production of glucose
4. Fat Metabolism- increased mobilization of fats

Question 9

Describe diabetogenic properties of GH

Answer 9

Hypophysectomy- reduction of hyperglycemia (since GH makes you hyperglycemic)

Insulin resistance often noted in pts with acromegaly

Question 10

How is GHBP produced?

Answer 10

GHBP is produced by proteolysis of GH receptor at cell surface–thus GHBP levels are indicative of GHR levels

Question 11

What type of dwarfism results from severe GH deficiency in children?

Answer 11

Proportional

Question 12

Describe Laron Syndrome

Answer 12

Autosomal recessive GH receptor variant–insensitivity to GH

Low levels of IGF associated with longevity and lack of cancer