Causes of hair loss
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Sex steroid hormones drive the development of androgenetic alopecia (also known as male pattern hair loss). These hormonal effects are largely influenced by genetics. However, there are many other reasons why your hair may be falling out.
Causes of hair loss include:
- abnormal levels of non-sex steroid hormones
- problems with diet and/or nutrition
- certain medical conditions or medications
- stress and other lifestyle factors.
In this article, we discuss these four factors, as well as the hair loss disorders they might trigger in greater detail. Since these conditions are all treated differently, it’s important to discuss any unusual shedding with a physician.
What hormones cause hair loss?
Dihydrotestosterone (DHT) is recognized as a primary cause of male pattern hair loss. DHT acts on the dermal papilla, the region of the hair follicle that controls the production of androgen (male sex steroid) receptors and the 5-alpha reductase enzyme. This increased hormonal activity triggers follicular miniaturization and eventually, hair loss.
In some men, normal levels of androgens are sufficient to trigger hair loss (Cranwell & Sinclair, 2016). This suggests that factors other than androgens may play a role. In fact, researchers have identified other hormones and hormone-like molecules that can affect the dermal papilla and cause changes in hair growth.
Examples of these molecules include: melatonin and thyroid hormones (Heilmann-Heimbach et al., 2020). Each of these molecules has the potential to bind to dermal papilla cells in the hair follicle and trigger biochemical changes. These changes can go on to impact cell growth and metabolism within the hair follicle and surrounding tissues.
Melatonin and hair
The melatonin supplements you take to help you fall asleep probably won’t cause your hair to grow back, but your skin cells’ ability to produce and metabolize melatonin, might.
Most people associate melatonin production with the pineal gland in the brain, but research has shown that other parts of the body, including skin cells, contribute to melatonin levels overall.
Melatonin may modify how androgen and estrogen (female sex steroid hormone) receptors respond to their respective hormones. Because sex steroid hormones are involved in transitioning between different stages of the hair growth cycle, melatonin could have an indirect effect on follicle cycling.
In laboratory studies, melatonin helped extend the active growth phase of hair and stimulated cell growth and proliferation (Fischer et al., 2007).
This may be due to the hormone’s antioxidant activity, which means that it helps the body eliminate byproducts of normal cell metabolism that might otherwise cause damage to healthy tissues (Fischer et al., 2007). At this stage, it’s unclear whether laboratory results can be replicated in individuals and if so, what the ideal dosing or format would be.
Do thyroid problems cause hair loss?
Yes, abnormal levels of thyroid hormones have been associated with hair loss. Thyroid hormones are produced by the thyroid gland at the front of the neck and help regulate metabolic activity of cells (van Beek et al., 2008).
Individuals with low or excessive levels of thyroid hormones may experience diffuse hair loss that looks like pattern hair loss, but the mechanisms are fundamentally different.
When thyroid hormone levels are optimal, cell growth and development proceed normally. In contrast, abnormal levels may lead to dry, brittle hairs and an increased number of hairs in the rest phase of the growth cycle (van Beek et al., 2008).
In many cases, hair loss associated with thyroid hormone imbalances is not restricted to the scalp. Individuals may notice thinning elsewhere on the body, including the eyebrows. Fortunately, thyroid hormone levels can be corrected with medication, micronutrient supplementation and improved stress management.
Can diet cause hair loss?
Possibly. We know that vitamins and minerals are important facilitators of the growth of hair follicles, but exactly which ones do and what their optimal levels are, is still a matter of debate (Almohanna et al., 2018).
While most people don’t have dietary deficiencies serious enough to cause extensive loss of hair, there are two micronutrients that are worth paying attention to: Vitamin D and iron. Your diet should include the daily recommended amounts of these micronutrients.
Vitamin D and hair loss
Low levels of vitamin D can cause hair loss. This vitamin is critical to the proper growth and maturation of hair follicle cells.
In a study of rickets type II patients, who represent cases of extreme vitamin D deficiency, the absence of this micronutrient resulted in hair loss that not only affected the scalp, but the rest of the body (Almohanna et al., 2018).
Vitamin D has known anti-inflammatory properties and plays an active role in regulating the immune system. It may help maintain the health of the scalp and hair follicles by ensuring that they are not mistaken for foreign tissue and damaged during periods of high stress (Almohanna et al., 2018). For these reasons, vitamin D is particularly important in the treatment of a type of hair loss called alopecia areata, an autoimmune disorder.
Iron and hair loss
Iron deficiency can also cause hair loss. The exact role of iron in hair growth is unclear, but researchers think it could be involved in the activation of proteins needed to duplicate DNA within cells (a necessary step before they can divide).
Iron may also help regulate genes specific to the hair follicle and therefore, the production of proteins that make up the developing hair shaft and surrounding tissues (Guo & Katta, 2017).
In 2002, a study found that a 6 month course of daily iron and L-lysine (an amino acid) supplements resulted in a statistically significant reduction in hair loss (2002). Another placebo-controlled study demonstrated a 31% reduction in the number of telogen (rest phase) hairs, compared to the placebo-treated group which saw only a 9% reduction (Rushton et al., 2002).
What illnesses and medications cause hair loss?
Certain health conditions, medications and even major surgery can be causes of hair loss. Systemic, chronic and inflammatory illnesses such as lupus, inflammatory bowel disease and psoriasis may cause diffuse shedding (Harrison & Bergfeld, 2009). These health conditions are associated with increases in chemical signalers that can damage healthy tissues over time.
Additionally, many common medications, such as those prescribed to control blood pressure and mood disorders, may trigger hair loss as a side effect.
Drug-induced hair loss is typically noticeable within 12 weeks of starting a medication and continues as long as one remains on therapy (Harrison & Bergeld, 2009). If you suspect that medication may be causing your hair loss, you must consult a physician prior to making any changes.
Aside from inflammatory disorders, fungal or bacterial infections may also cause hair loss. The latter are often accompanied by scalp redness, sores, lesions or swollen glands and should be examined and treated by a physician (Phillips et al., 2017). One example is Tinea capitis, a common fungal infection that results in patchy bald spots that usually resolves with the help of an oral or topical antifungal.
What about depression and hair loss?
While a direct link between depression and hair loss has not yet been established, prior research suggests that there may be a relationship between antidepressant use and hair loss. These medications may result in imbalances in molecules that have a downstream effect on the body’s ability to make other hormones (e.g. melatonin) (Fischer et al., 2012).
Can stress cause hair loss?
Absolutely. Periods of stress are accompanied by increased secretion of corticotropin-releasing hormone (CRH) in the brain. CRH is a molecule that triggers inflammation, as well as the downstream production of the stress hormone, cortisol.
Inflammation is part of the immune response. It’s counterproductive to hair growth because it encourages hair follicles to move into the catagen (regression) phase of the hair growth cycle.
During the regression phase, the follicle stops producing the hair fibre and shrinks in preparation for the rest phase (Heilmann-Heimbach et al., 2020). Early regression has been linked to the production of shorter, weaker hairs. When this happens en masse, telogen effluvium, or sudden stress-related shedding, may occur.
In addition to this, high levels of stress hormones may interfere with cell signaling pathways and accelerate the breakdown of key structural components of skin, such as proteoglycans and hyaluronan (Thom, 2016). You could start noticing dryer, itchier skin or changes in hair texture as a result.
While androgens such as DHT are associated with premature shedding, it is important not to overlook other causes of hair loss. Based on the discussion above, it’s clear that not all hair loss requires pharmaceutical intervention.
In some cases, lifestyle adjustments can have positive effects on your hair and beyond. This is why it’s important to keep your physician up to date about any changes to your health, including increased shedding. This proactive approach can help ensure that any issues are promptly identified and treated if necessary.
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