Pituitary Physiology & Pharmacology- Teresa Flashcards
What are the hormones in the growth hormone axis?
Hypothalamus: GHRH and somatostatin (GHIH), also dopamine which is inhibitory
Pituitary: GH
What type of receptor is the GHRH receptor?
GPCR- Gas
How does somatostatin work?
Via SSTR-1 through -5 which are G-inhibitory GPCRs
Where is GH made ?
Anterior pituitary- somatotrophs (acidophils)
What is GH bound to in the serum?
GH binding protein (GHBP)
Level of GHBP indicates tissue levels of GH receptor since it is the ectodomain of GH receptor
What is the GH receptor on target cells?
Transmembrane, cytokine receptor that activates JAK/STAT pathway
What does liver produce in response to GH?
IGF-1 (somatomedin)
What are the actions of GH?
- Protein Metabolism- increase aa uptake and protein synthesis
- Mineral Metabolism- increase mineral density in bones
- Carbohydrate Metabolism- decrease carb utiliztion–>hyerglycemia d/t reduced uptake of glucose and increase liver production of glucose
- Fat Metabolism- increased mobilization of fats
Describe diabetogenic properties of GH
Hypophysectomy- reduction of hyperglycemia (since GH makes you hyperglycemic)
Insulin resistance often noted in pts with acromegaly
How is GHBP produced?
GHBP is produced by proteolysis of GH receptor at cell surface–thus GHBP levels are indicative of GHR levels
What type of dwarfism results from severe GH deficiency in children?
Proportional
Describe Laron Syndrome
Autosomal recessive GH receptor variant–insensitivity to GH
Low levels of IGF associated with longevity and lack of cancer
