Hair loss or alopecia can be devastating. Though it is relatively “benign,” it creates a great deal of emotional distress and lower quality of life for those who experience it. What can be equally or more upsetting is the lack of understanding and solutions surrounding hair loss. In recent years, technology has allowed for a deeper study of the environment of the hair follicle and the things that impact it both positively and negatively. It is important to note that hair loss is multi directional and multifactorial; there may be imbalances that indirectly drive hair loss and multiple contributing factors that may occur independently or overlap and occur in conjunction with other factors. Up until recently, the different hair loss triggers and solutions were mainly focused on the effect of androgens on hair but we are now able to see other hormone imbalances, stress, digestion, increased inflammation from infections, environmental exposures (systemically and locally) and poor blood sugar regulation may all contribute as well. Using a holistic lens, the mechanisms behind these types of hair loss will be discussed.
The Growth Cycle
Understanding normal functioning of the hair growth cycle is an important part of understanding hair loss. There are 3 key phases: anagen, catagen and telogen. Anagen is known as the growth phase and this phase lasts anywhere from 2 to 7 years. At any given time, most hairs are in the anagen phase of the cycle (80- 90% of hair). In order for hair to stay in this phase and for hair to grow, it requires adequate blood flow, oxygen and nutrients. Catagen is known as the transition phase that is mediated by apoptosis, or cell death, and it is when all growth stops. This phase lasts approximately 2 to 3 weeks. Telogen lasts 3 to 6 months and is the resting phase where the hair is getting ready to shed; 5-10% of hair is in this phase. Exogen is the active shed where the hair is finally expelled. Some less common phases are kenogen which is the period between resting/shedding and growth of new hair also known as a dormant phase. Note that shedding is part of a normal and healthy hair growth cycle (1).
Hormones and Hair Loss
Hormone-driven hair loss is known as androgenetic alopecia and often referred to as female or male pattern hair loss. The hormone responsible for loss of scalp hair is dihydrotestosterone (DHT), an androgen which has a higher affinity for androgen receptors than testosterone making it 10 times more potent than testosterone when bound to an androgen receptor (2). What makes this interesting is that you may not necessarily have elevated androgens or DHT on labs, however your receptors may have a higher affinity for DHT. Essentially, your body will hold more tightly to whatever DHT is around. This is often due to genetic predisposition. However, there is an enzyme called 5-alpha reductase which is responsible for converting testosterone to DHT and activity of this enzyme can be mitigated via diet and lifestyle. Elevated DHT levels inhibit anagen and promote telogen. (3)
Low thyroid hormone impacts hair as well by making hair more brittle and susceptible to breakage (4). A less studied hormonal imbalance that could be implicated in hair loss is that of low progesterone. Whether this influences androgenic hair loss or even the hair growth cycle is still unclear. However it may indirectly impact hair loss due to the inherent antioxidant and anti-inflammatory properties of progesterone. Lower levels of progesterone are associated with higher levels of systemic inflammation (5). Circulation of systemic inflammatory chemicals inhibit anagen, promote telogen as well as catagen.
It is this effect of inflammation on the hair cycle coupled with stress that is responsible for post-viral shedding that many notice after having had COVID19. It is important to note that this response to inflammation can happen after any illness or infection (whether hidden or overt) that inflicts marked inflammation and stress (6). Inflammation and the reactive oxidative species produced as a result are significant triggers of damage to the hair follicle.
Hair loss can also be mediated by stress hormones and their chemicals. Most people only think of emotional stress but there are also sources that lead to physiologic stress within the body such as: medications, toxic exposures from the environment, inflammation, febrile conditions, extreme weight fluctuations, childbirth, surgical procedures, chronic diseases. The emotional distress surrounding hair loss then perpetuates the cycle of loss (compounded with any other life stresses!) due to the further release of stress hormones. Identity, confidence, vitality are all properties that people have mentioned to me that they associate with their hair. Someone once expressed to me that their hair loss deepened their grief that had triggered their hair loss in the first place.
Hair is impacted by the continuous release of stress hormones and their downstream mediators both systemically as well as at the level of the hair follicle (7). This leads to a disruption of the hair growth cycle, shifting hair out of anagen and into catagen. Essentially less time is spent in the growing phase and more time is spent in cell death, resting and shedding (8). The type of hair loss mainly associated with stress is telogen effluvium and it is characterized by bouts of shedding of more than 100 hairs per day typically starting on average 3 months after a stressful event (9). Chronic stress has impacts on many other systems that end up negatively affecting hair as well. Some examples of the downstream effects of stress impacting hair include: increased inflammatory chemicals, increased insulin and blood sugar secretion, decreased stomach acid production, decreased thyroid hormone function and production. As mentioned earlier, when thyroid hormones are low, hair becomes more brittle. Higher levels of insulin lead to more circulation of inflammatory cytokines and DHT. Low stomach acid impairs adequate digestion and absorption of protein, a major building a block for the collagenous structural component of hair. The good news is, hair loss due to telogen effluvium is typically non-scarring and has a high likelihood of regrowth (10).
The hair follicle requires specific nutrients for growth and as such, deficiencies of these nutrients negatively impact hair. Proteins, vitamins, minerals and fatty acids are all critical for healthy hair. Inadequate nutrition, whether due to insufficient access, dietary habits, malnutrition, maldigestion/malabsorption all may end up being another trigger for hair loss because the hair follicle is not getting the nutrients it requires (11). Hair is largely made up of proteins, necessitating the role of adequate protein intake as well as adequate digestion and absorption of proteins when addressing hair loss. Micronutrients also play a role in hair loss. Biotin is the main micronutrient people assume is needed to address hair loss, but biotin is not helpful unless there is a biotin deficiency (12). Iron is another deficiency commonly associated with hair loss however not all hair loss improves with iron supplementation and screening for iron deficiency should be assessed first. Taking iron without specific indication can lead to iron overload as well as unpleasant side effects and without improvement of hair concerns; for this reason caution is advised with hair supplements containing iron unless recommended by your doctor. Vitamin D deficiency has been implicated in playing a role in alopecia areata, a type of hair loss characterized by patchy loss on the scalp and/or body (13). Low levels of vitamin D are also associated with autoimmune conditions including autoimmune thyroid disease (14). B vitamins and minerals are necessary cofactors for conversion of T4, inactive thyroid hormone, to T3, active thyroid hormone. And this conversion process largely happens in the digestive tract. Thyroid imbalances independently influence hair but can also be exacerbated by nutrient deficiencies and poor digestive health. These examples highlight the multifactorial, multidirectional and overlapping triggers that affect hair.
Exposures from the environment are yet another trigger for hair loss. Both systemic and local exposures can affect the hair follicle and normal functioning of the hair growth cycle. Mercury is one such exposure that has a strong association with alopecia (15). The impact on the hair follicle is likely due to the increased circulation of reactive oxidative species and is problematic if ingested from food or via dermal exposure from air or water (16). Tobacco is another exposure that impacts hair not only because of increased oxidative stress but also because of its effects of decreased circulation to the hair follicle. Other fairly common environmental exposures that increase oxidative damage to the hair follicle include alcohol and ultraviolet radiation (17).
While there are few direct influences on hair, advances in science and research allow us to better understand the environment of the hair follicle including the multiple triggers that influence hair, beyond simply genetics. Hair loss is multifactorial and multidirectional requiring a thorough assessment to address the root cause(s).