What indicates the end of the anagen phase in hair growth?

The anagen phase is the active growth phase of hair follicles, during which the hair strands are continuously produced and lengthened. The end of this phase is marked by a transition into the catagen phase, which is a short transitional stage where hair growth slows down, and the hair follicle begins to shrink.

During the catagen phase, the cells in the hair follicle undergo changes that prepare them for the next phase of the hair growth cycle, the telogen phase. This transition signifies that the hair growth has reached its peak, and the follicle will no longer produce hair until it is reactivated in a future anagen phase. The other options, such as growth slowing, hair loss, or thinning, can be indicators of various issues but do not specifically denote the transition from the anagen phase to the catagen phase. The key factor is that the necessary physiological changes occur for the hair to transition between these distinct phases of the growth cycle.