Parathyroid Hormone-Related Peptide and the Hair Cycle: Is It the Agonists or the Antagonists That Cause Hair Growth?

The document reviewed studies on the role of parathyroid hormone-related peptide (PTHRP) in the hair cycle, indicating that PTHRP agonists linked to a collagen binding domain can stimulate hair regrowth, particularly in damaged hair follicles, by accelerating the transition to the anagen phase. In contrast, PTHRP antagonists were found to initially prolong the anagen phase, leading to a short-term increase in hair growth, but ultimately inhibited normal hair regrowth by preventing follicles from re-entering the anagen phase. The overall effect of PTHRP is to stimulate and accelerate the hair cycle, with agonists promoting hair growth in certain conditions, such as damaged follicles, while antagonists can inhibit the hair cycle and reduce hair growth over the long term.