Understanding the Hair Growth Cycle

Hair follicles go through a cyclical process for growth. When we have a better understanding of the hair growth cycle, we can determine what impacts each stage and identify areas of needed attention. The four phases of the hair growth cycle include Anagen, Cataden, Telogen, and Exogen. The information below goes into further detail about what happens during each stage of this process. 

Anagen Phase (Growth Phase)

The anagen phase is the active growth phase of the hair follicle. During anagen, cells in the hair bulb divide rapidly, leading to the formation of new hair. The hair shaft grows longer at a rate of about half an inch (1.25 cm) per month on average. The anagen phase typically lasts between 3-5 years for hair on the head, and about 90% of head hair is in the anagen phase at any given time. This phase differs for hair on different parts of the body.

What factors impact the anagen phase?

The following factors can influence the amount of time and quality of growth during the anagen phase. 

  • Genetics
  • Age
  • Hormones
  • Health and Nutrition
  • Medical conditions and medications
  • Stress

Catagen Phase (Transitional Phase)

After the anagen phase, the hair follicle enters the catagen phase, which is a transitional phase that lasts for a few weeks. During catagen, the hair follicle shrinks and detaches from the blood supply. The hair in this stage is known as ‘club hair’, where it is no longer actively growing. The hair follicle changes during this short phase, where the lower portion becomes narrower. Although it is a short period, the catagen phase is an essential transition for healthy hair turnover between growth and rest. 

Telogen Phase (Resting Phase) 

The telogen phase is a resting phase that lasts for several weeks to a few months. During this phase, the hair follicle is dormant and doesn’t grow. Approximately 10-15% of hairs are in the telogen phase at any given time. While in this phase, the old hair is still attached to the follicle but is no longer growing.

Exogen Phase (Shedding Phase)

The exogen phase is often considered an extension of the telogen phase. During the exogen phase, the old hair that was in the telogen phase is shed as new hair begins to grow underneath it in the anagen phase. Shedding is a normal part of the hair growth cycle and is necessary for the growth of new, healthy hair. An estimated 50-100 hairs are shed per day, which is considered to be a normal amount. 

After the exogen phase, the cycle typically repeats itself, with a new hair strand growing from the same follicle. It’s important to note that not all hairs on your scalp are in the same stage of the cycle at the same time. This is why you normally don’t notice shedding or thinning, as there is a constant turnover of hairs in different stages of the cycle.

Disruptions in the hair growth cycle

Various conditions and factors can contribute to the disruption of the hair growth cycle. If you are experiencing excessive hair loss or thinning, talk to a doctor. At Regenerative Medical Institute, we offer a number of services to address hair loss and thinning, including hair restoration treatment plans and bioidentical hormone replacement therapy. Visit our website or call us for a free consultation: 877-573-3737.