It is always a good idea to understand what a healthy hair follicle cycle looks like in order to grasp what an abnormal one would be. A healthy hair follicle passes through three consecutive stages in each cycle, which include proliferation (anagen), involution (catagen), and resting (telogen).
A healthy anagen phase takes from two to six years and interestingly not only is the hair shaft growing, but also most epithelial hair follicle compartments undergo proliferation as well. The highest proliferative activity is experienced by the hair matrix keratinocytes.
During the catagen phase, the hair follicle enters a process of programmed cell death with an upward movement of the follicle, followed by a telogen phase that lasts approximately 100 days, where shedding of the hair takes place and new hair grows on in the anagen phase (1).
In fact, hair follicles follow a random mosaic pattern of growth where each follicle has its own rhythm, uninfluenced by the follicles immediately surrounding it. (2). However, On average, the total number of new hair formations compensates for the amount of hair that is shed, so the total number of hair covering the scalp remains consistent.
With a range of 75 000 to 150 000 hairs on the head, the reported average daily telogen hair shedding varies from under 50 to over 100 in a healthy individual.
When Does Postpartum Hair Loss Start and What Is The Mechanism Behind It?
Clinically, postpartum hair loss is classified as a subgroup of the telogen effluvium hair loss, and more specifically considered an acute type of telogen effluvium which means a new mother is losing < 50 % of scalp hair that takes a place around 3 months after postpartum. A study by Kligman reported that scalp hair loss may be up to 400 hairs daily during the postpartum period. (3).
You might be surprised to know that postpartum hair loss is a normal physiological response to hormonal alterations, however, it can be an extremely frightening experience! No one enjoys seeing their hair fall out! In contrast to pregnancy, where a combination of hormonal changes can increase the number of hair follicles and promote thicker, shinier hair, the removal of the placenta at birth causes levels of progesterone and estrogens to return to normal within 2-4 days and more hair is shed. Scientifically speaking, during pregnancy the thyroid hormone, secondary androgen, and estrogens hormones can cause hair follicles to remain in the anagen phase allowing for more hair to grow, whereas after a women has given birth a higher number of hair follicles enter the telogen phase leading to a higher than usual number of hairs being shed.