Hair growth in each hair follicle occurs in a cycle. There are three main phases of the hair growth cycle: anagen, catagen and telogen.

1. Anagen (active) is the growing phase or when the hair fiber is produced.
2. Catagen (club hair) is the period of controlled regression of the hair follicle. This phase is when the lower part of the hair stops growing, but does not shed, and the follicle is reabsorbed.
3. Telogen (tired) is the last of the hair growth cycle. In this resting phase, the old hair falls out in preparation for the development of a new anagen hair.

Normally this cycle of hair production will continue for the duration of the individual’s life. However, various factors can influence, promote and inhibit hair production.