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. Author manuscript; available in PMC: 2017 Aug 1.
Published in final edited form as: Growth Horm IGF Res. 2016 Apr 7;29:21–27. doi: 10.1016/j.ghir.2016.03.005

Figure 4. Schematic diagram of GH, IGF-I, and Humanin regulation.

Figure 4

GHRH stimulates pituitary GH release which stimulates IGF-I production mainly in the liver. IGF-I forms negative feedback loop to GH release by stimulating SRIF, which inhibits pituitary GH release, and by inhibiting pituitary GH release directly. IGF-I suppresses humanin level in the plasma, and vice versa humanin suppresses circulating IGF-I level. Both IGF-I and humanin binds to IGFBP-3. Somatotropin release-inhibiting factor (SRIF); GH-releasing hormone (GHRH)