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What's going on in hair loss?

What's going on in hair loss?

In our last article ‘what’s up with hair dyes’ we started exploring the topic of the hair cycle. Today, we will be expanding on that topic by including a discussion on hair loss. However, in order to know how hair is lost, we need to first understand how hair grows.

Hair cycle

For a quick summary of the hair cycle, check out our last article! ‘link’

Anagen phase

This is the growth phase where hair is constantly being produced from the follicle at a rate of roughly 15 cm per year lasting 3-4 years. This means that on average, a person’s maximum hair length is usually between 45 to 60 cm. Of course, we’ve all seen individuals with hair lengths that greatly exceed these numbers and that’s because these rates vary depending on individual genetics and health conditions. We also know that specific hormones can play an important role in determining hair growth and even hair quality. However, while there are some suggestions that hair growth varies based on sun exposure, nutritional supplements (not to be confused with physiologic nutritional needs), and season, these are not based on strong evidence and are more likely to be myths.

Catagen phase

This is the transitional phase that precedes the telogen phase. During this 1-2 week long phase, the hair follicle shrinks in size, slows down hair production, and slowly pushes the root of the hair out of the skin.

Telogen phase

This is the resting phase of the hair follicle. The hair is completely pushed out of the skin and the hair follicle becomes inactive for up to 4 months. While this is the natural cycle, there are triggers that can cause this cycle to happen more rapidly (discussed below).

Wait a minute, if this is all true, then why don’t our heads become completely bald for 4 months every 3 years? That’s because your hairs are usually all at different parts of the hair cycle, meaning that while some hair is lost everyday, other hairs grow in their place. In fact, it’s completely normal to lose between 50-100 hairs a day just from the hair cycle.

Types of hair loss

Everyone loses hair for different reasons over time. As we age, our hair follicles age with us and if you track an individual`s photos over a period of decades, you may notice that they usually appear to have less hair. This is due to a combination of reduced number of hairs, reduced thickness of hairs, and change in hairline. However, the way hair changes over time depends on the cause. For instance, gender can play a crucial role is how hair is lost.

Male pattern hair loss

In men, hair loss classically manifests as a receding hairline starting from the front with overall loss of hair on the top of the scalp. Overtime, they can become completely bald on the top of their heads with only a ring horseshoe shaped rim of hair. Give it enough time and that can disappear too. Of course, not every man develops complete baldness during their lifetime and where an individual sits on the hair loss spectrum depends on their genetics. There is good scientific evidence that male pattern hair loss is linked to a type of testosterone called DHT. While men naturally produce significant levels of DHT, there are many medical conditions that can also produce an abnormal amount of DHT thus triggering this type of hair loss in men and women.

Female pattern hair loss

Individuals that experience female pattern hair loss typically don`t have receding hairlines. Instead, they have generalized thinning and reduced density all over their scalp. Interestingly, it rarely leads to complete baldness. Furthermore, we don`t fully understand the biological mechanisms that cause female pattern hair loss.

Stress related hair loss

The medical term for this is telogen effluvium and simplistically speaking, it can be caused by various types of stress, including hormonal stress, physical stress, emotional stress, etc. This type of hair loss looks like generalized shedding of the hair follicles but it doesn`t occur right after the stressor. Instead, it actually happens several months after. The reason for this is in the name, telogen effluvium. When you experience sufficient stress, your hair follicles actually jump straight into the telogen phase and stop growing so for the next several months during this phase, your hair will just sit there. When your follicle finally decides to reactivate hair growth (enter anagen phase), it will push out the current hair and cause generalized shedding. Fortunately, this type of hair loss is generally not permanent.

External damage related hair loss

In our last article, `what`s up with hair dyes`, we mentioned that there isn`t much evidence that suggest hair loss as a result of using hair dyes. While this true for hair dyes, we can`t say the same for some of the other things that we do to our hair, intentionally or accidentally. These can be from mechanical damage, like very tight hair braids, doing head spins in break dancing, and hair pulling, from heat damage, like hair straightening, hot combing, and blow dryers, and from microbial damage like bacterial or fungal infections.

Nutritional deficiency related hair loss

Believe it or not, to some extent, your body naturally prioritizes your organs. Hair, as you may expect, is not very high up on that list. Therefore, when your body senses signs of nutritional deficiencies, such as when you have significant weight loss, missing specific vitamins or nutrients, or when it doesn`t get enough protein, it may shut off hair production to conserve energy.

Medical causes of hair loss

This topic is a whole can of worms on its own and is definitely beyond the scope of today`s article. But just as a brief summary, there are many medical illnesses that can manifest in hair loss. These causes include, among others, autoimmune, inflammatory, and infectious. While some of these are reversible, like alopecia areata (an autoimmune cause of hair loss), others can cause scars and thus prevent regrowth of hair by obliterating the hair follicle.

How do the most common therapies for hair loss work?

While there are many medical and surgical therapies for hair loss, these topics are specific to the patient and type of hair loss. Therefore, we will only be focusing on two of the most commonly known treatments, both of which treat male pattern hair loss.


Minoxidil, or better known by one of its brand names Rogaine ©, is one of the most researched hair loss drugs out there and is the most commonly available over-the-counter hair loss medication. Even though it is a drug that we have had for decades, we still don’t fully understand how it causes hair regrowth in humans. From what we do understand, it is a vasodilator (dilates blood vessels) and there is some evidence that it transitions the hair follicle into anagen phase, prolongs the anagen phase, shortens the telogen phase, and widen the follicle. The overall combined effect would generate an image of increased hair density and fullness. It is primarily used in male pattern hair loss.


Finasteride, or Propecia ©, is perhaps the second most commonly known hair loss drug. It works by blocking the production of DHT, which, as we mentioned above, causes male pattern hair loss. In general, it’s not as well tolerated as minoxidil.

Let’s sum it up!

Hair loss can be stressful, not to mention stress itself can cause hair loss in return. While it is actually a really big topic (there are whole textbooks written on it), we’ve tried to summarize the basics of the topic and hope that you found it useful!

That’s all for today folks!


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