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. 2021 Dec 8;22(24):13205. doi: 10.3390/ijms222413205

Figure 1.

Figure 1

Schematic representation of the HPS axis interacting with the human hair follicle. In the HPS axis, GHRH acts on the GHRHRs in somatotropic cells of the anterior pituitary to release GH systemically, which interacts with GHRs systemically, including in the HF. GHR activation increases IGF-1 transcription, which exhibits negative feedback on GH synthesis in the anterior pituitary and GHRH synthesis in the hypothalamus. GHRs have been found in the human HF. Stimulation of GHRs in HFs ex vivo has shown to inhibit hair growth in female human scalp HFs via upregulation of TGF-β2 (Alam, et al., 2019). HPS = hypothalamic-pituitary-somatotropic, GH = Growth Hormone, GHR = Growth Hormone Receptor, GHRH = Growth Hormone-Releasing Hormone, GHRHR = Growth Hormone-Releasing Hormone Receptor, IGF-1 = Insulin-like Growth Factor-1, TGF-β = transforming growth factor β.