Thyrotropin-Releasing Hormone and Hair Growth
Tuesday, October 20th, 2009
In the study of hair growth and hair elongation, there’s a new kid on the block. He goes by “TRH” or, to be more specific, Thyrotropin-Releasing Hormone. TRH has the potential to play a major role in Hair Restoration and Hair Transplants.
This month, a new discovery in hair growth and the hair growth cycle was published in the Journal of the Federation of American Societies for Experimental Biology. The study was done in Germany by Dr. Gaspar at the University of Lübeck, Department of Dermatology and Department of Internal Medicine.
Thyrotropin-Releasing Hormone (TRH) has proven to be one of the factors involved in the hair follicle growth cycle. Thyrotropin-Releasing Hormone is in closest proximity to the hypothalamic-pituitary-thyroid axis, which regulates thyroid hormone synthesis.
Since transcripts for members of this axis were detected in normal cultured human skin cells, and because it’s been found that when human hair follicles (HFs) are stimulated with thyrotropin, they respond, researchers have decided to study whether human hair follicle functions are also modulated by thyrotropin-releasing hormone. They report that the epithelium of normal human scalp hair follicles expresses not only TRH receptors (TRH-R), but also TRH itself at the gene and protein level.
Stimulation of micro-dissected, organ-cultured hair growth with thyrotropin-releasing hormone promotes hair shaft elongation, prolongs the hair cycle growth phase (anagen), and antagonizes its termination by TGF-beta2. It also increases proliferation and inhibits the apoptosis of hair matrix keratinocytes. These Thyrotropin-Releasing Hormone effects may be mediated in part by reducing the ATM/ATR-dependent phosphorylation of P53. By microarray analysis, several differentiated up-or down-regulated TRH-target genes were detected (e.g., selected keratins).
Thus, human scalp follicles are both a source and a target of thyrotropin-releasing hormone, which operate as a potent hair-growth stimulator. Human hair follicles are an excellent discovery tool for identifying and dissecting non-classical functions of thyrotropin-releasing hormone and TRH-mediated signaling, which emerge as players in human epithelial biology.
