Page Contents
OVERVIEW
This page focuses on the hormonal pathways that control the production of growth hormone (GH). GH is very important for bone, muscle, and organ growth and development.
![Human growth hormone (HGH) signaling pathway (source)](http://www.stepwards.com/wp-content/uploads/2016/02/how-gh-works.jpg)
HYPOTHALAMUS
The hypothalamus starts off this hormonal pathway by the release of GH-releasing hormone (GHRH). When this hormone is released by the hypothalamus it acts on the anterior pituitary to release growth hormone (GH)
Factors that increase GHRH secretion include the following:
- Puberty
- Exercise
- Sleep (circadian rhythms)
Factors that decrease GHRH secretion include the following:
- Insulin-like growth factors (ex. IGF-1)
ANTERIOR PITUITARY
The anterior pituitary continues this signaling pathway by releasing GH (which in turn acts on the liver to release insulin-like growth factors)
Factors that increase GH secretion include the following:
- GHRH
- Estrogen
Factors that decrease GH secretion include the following:
- Somatostatin
- Insulin-like growth factors (ex. IGF-1)
- Glucose
LIVER
GH acts on the liver to produce insulin-like growth factors (common example is IGF-1).
WHAT DO INSULIN-LIKE GROWTH FACTORS (IGF-1) DO?
The actions of GH are mediated through hormones like IGF-1 who have the following activity:
- Promote linear bone development in individuals who have the growth plates of long bones still open
- Stimulate muscle growth
- Increase insulin resistance
- Feed back inhibition on the GH hormone axis (at the level of the hypothalamus and anterior pituitary).
Page Updated: 02.20.2016