Endocrine Regulation of Growth ✅ Flashcards
What exerts the major influence on post-natal growth?
Growth hormone
What kind of molecule is growth hormone?
An amino-acid polypeptide
How does growth hormone exist in the circulation?
Bound to a GH-binding protein
What is the GH-binding protein derived form?
The extracellular component of the GH receptor
Where is GH secreted from?
Somatotroph cells
What regulates the secretion of GH?
Dual control of;
- GH releasing hormone
- Somatostatin
Where is GH-releasing hormone and somatostatin secreted from?
The hypothalamus
Why is dual regulation of GH required?
To produce episodic pulses
At what time of day is GH-releasing hormone and somatostatin released?
Mostly at night
What regulates the release of GH-releasing hormone and somatostatin?
Central neurotransmitters
What stimuli do central neurotransmitters causing release of GH-releasing hormone and somatostatin respond to?
- Nutrition
- Sleep
- Exercise
- Stress
Where does GH act?
Liver and a number of other organs
What does GH stimulate in the liver and other organs?
The synthesis of insulin-like growth factors (IGF-1 and IGF-2)
What is the similarity between insulin-like growth factors and insulin?
They share a degree of structural homology with proinsulin, and may exert weak insulin-like effects
How does IGF-1 circulate?
Bound to IGF binding protein (IGFBP-3)
What regulates the concentrations of IGFBP-3 in the circulation)
GH
What happens to the IGF-1 - IGFBP-3 complex in the circulation?
It associates with an acid-labile subunit, and the combination forms a ternary complex
What is the acid-labile subunit?
Another GH-dependent glycoprotein
Is IGF-1 active when bound?
No
What is the effect of IGFBP on the half-life of IGF?
It prolongs it
What does the prolonged half life of IGFs when bound to IGFBPs allow?
Transport to target cells
Where are the target cells for IGF?
In the growth plate
What happens when IGF interacts with their target cells in the growth plat?
They interact with IGF receptors to produce biological effects
