What characterizes the catagen phase of hair growth?

The catagen phase is a transitional stage in the hair growth cycle, marking the end of the active growth phase known as anagen. During catagen, the hair follicles undergo significant changes, including the shrinking of the hair shaft. This is characterized by the hair shrinking to approximately one-sixth of its original size as it detaches from the actively growing follicle.

In this phase, the hair follicle undergoes apoptosis (programmed cell death), and the hair begins to enter a resting state. This stage lasts for a relatively short period, typically several weeks, after which the hair follicle will enter the telogen phase, in which hair remains in a resting state before eventual shedding.

The other processes, such as speeding up growth or becoming inactive, do not accurately describe what happens during catagen. Instead, this phase is distinctly characterized by the structural changes in the hair and follicle, indicating its transition toward the shedding of the hair strand in the next phase.