Estrogen Leads to Reversible Hair Cycle Retardation Through Inducing Premature Catagen and Maintaining Telogen

The 2012 study found that estrogen, a hormone, can cause a delay in the hair growth cycle by inducing the premature onset of the catagen phase (where hair stops growing) and maintaining the telogen phase (where hair falls out). This results in a retardation of hair growth. However, this effect was found to be reversible once the influence of estrogen was removed. The study also found that estrogen induced apoptosis of precortex cells, leading to premature catagen by up-regulating TGF β2 and increasing the expression of BMP4, potentially preventing anagen transition (the growth phase) and maintaining telogen. Despite these changes, the hair follicle stem cell niche was not destroyed, suggesting that the hair loss caused by estrogen might be a nonscarring type of alopecia and could be reversible. The study did not mention the number of participants involved.