How Testosterone Affects Hair: Does It Make You Lose Hair?

 Key takeaways:

• Testosterone is an androgen that plays a significant role in hair development in various body parts.
• However, testosterone and its derivative, dihydrotestosterone (DHT), can make a person lose hair on their scalp.
• Women may also experience pattern baldness due to androgens. 
• Other causes of hair loss include hormonal changes, certain medications, poor nutrition, and autoimmune conditions such as alopecia areata.

It’s pretty well-known among medical experts that testosterone and dihydrotestosterone (DHT) play a major role in male pattern baldness. Both testosterone and DHT are androgens, i.e., sex hormones that modulate the development of adult male sex characteristics, including hair growth. 

During puberty, androgens kick in, transforming light, tiny hairs on your body into thicker, darker hairs. But guess what? Men aren’t the only ones with these hormones. Women also have androgens, just in smaller amounts. 

How does testosterone stimulate hair growth in some parts of the body while leading to hair loss in others? And can women also experience this type of hair loss? Keep reading to find out. 

 How testosterone affects hair on different parts of the body

Testosterone is the major male hormone. However, it typically works with a more active product, dihydrotestosterone (DHT).

Testosterone is converted to DHT by the 5-alpha reductase enzyme, which is present in various body tissues. These androgens influence hair growth, especially during puberty, but their effects depend on the tissues involved.

During puberty, testosterone and DHT stimulate the growth of facial hair, body hair, and pubic hair. Therefore, men who lack testosterone or the enzyme 5-alpha reductase to produce the active metabolite DHT generally have poor beard growth.

Androgens can affect hairs thanks to receptors at the dermal papillae found at the base of each hair follicle. By binding to these sites, these hormones stimulate hair growth in these areas.

But while testosterone can stimulate hair growth in most parts of the body, it conversely retards hair growth on the scalp when it binds to hair follicles in the head, leading to hair loss or baldness.

 Overview of the hair growth cycle

Fun fact: The hair you see projecting out of your skin is actually dead. The hair strand is made up of dead, hardened cells filled with the protein keratin. The living portion of your hair is the hair follicle, which is buried underneath your skin.

Hair follicles go through various cycles of growth to produce visible hair. The events in this cycle are divided into separate but continuous stages, namely the growing phase (anagen), regression phase (catagen), resting phase (telogen), and shedding phase (exogen).

• The anagen phase: This is the longest phase of the hair cycle, lasting between two and seven years. During this phase, which is also called the growing phase, the cells in the follicle divide rapidly.  
• The catagen phase: Here, the hair shaft disconnects from the dermal papillae and contracts, so it’s also called the regression phase. This is a shorter period, lasting only about three weeks.
• The telogen phase: This is also called the resting phase and is characterized by the retraction of the dermal papilla. It is essentially a quiet phase, lasting about three months, during which the cells are neither dividing nor dying.  
• The exogen phase: This is the final phase of the hair cycle, also called the shedding phase. During this phase, old hairs fall out while new hair grows within the follicles.  

At any given time, about 85–90% of the hair on your scalp is in the anagen phase, while the rest may be in either the catagen or telogen phases.

 Understanding the role DHT plays in male and female pattern baldness

In adults, about 10% of the testosterone is converted into DHT, a central player in male pattern baldness. Since males have more testosterone than females, they naturally have more DHT.

Pattern baldness, also called androgenetic alopecia (AGA), is the most common reason men lose scalp hair. It occurs in women, too, but to a lesser extent. At least 80% of men and 50% of women by age 70 are affected by this condition.

There is evidence to show that this type of baldness is hereditary. This means that a bald father is likely to have bald sons. That chance is as high as 80%.

Unlike non-balding men, bald men have high levels of DHT on their scalp. This suggests that AGA may result from the action of DHT on follicular androgen receptors.

In people with baldness genes, DHT binds to the androgen receptors within the scalp’s hair follicles. These receptors respond by shortening the anagen, or growth phase, within the normal hair growth cycle.

This repeated shortening of the anagen phase soon causes the large, terminal hair follicles to become thinner and shorter, a process known as follicular miniaturization. As a result of these factors, these transformed follicles produce short, fine hairs that are not long enough to reach the scalp's surface, hence baldness.

Persons with androgenetic alopecia have high levels of 5 alpha-reductase and dihydrotestosterone (DHT). They also have increased androgen receptors in the areas of the scalp affected by balding.

In males, hair loss is more obvious at the top of the head and hairline, especially in the temporal region. In females, it affects the crown and top of the head, preserving their frontal hairline. These are termed male-pattern and female-pattern hair loss, respectively.

 Other possible causes of baldness

Aside from the effects of DHT, other things that can cause baldness include:

 Alopecia areata

Alopecia areata is a disease in which the body’s immune system attacks hair follicles, causing hair loss. Alopecia areata usually affects the head and face but can also affect any body part. It is a relatively common disease, affecting up to 2% of the general population.

 Hormonal deficiencies

Androgens aren’t the only hormones that regulate hair growth. Other hormones like estrogen and thyroid hormone play essential roles, so their unavailability will hinder their contribution to hair development. Let’s look at how these hormones function in hair growth:

• Estrogen: Oestrogen, produced by the ovaries, is vital for the growth of axillary and pubic hair in females. After menopause, there is a drop in estrogen production because of a decline in ovarian follicles. This leads to an increased frequency of female pattern hair loss in this group.
• Growth Hormone: Growth hormone works together with androgens to influence sexual hair growth. Hypogonadal men (with low testosterone) require more testosterone supplementation to stimulate axillary hair growth if they also have growth hormone deficiency.
• Prolactin: In females, prolactin aids hair lengthening in the fronto-temporal region of the scalp. In males, it stimulates catagen in the hair follicles of the occipital scalp.
• Melatonin: Melatonin affects hair growth by accelerating the anagen phase. It also helps to protect hair follicles from oxidative stress.
• Thyroid: The thyroid hormone regulates the frequency of the hair growth cycle. Low levels of thyroid hormone have been linked with decreased anagen frequency.

Other factors like anti-cancer drugs, radiation, poor nutrition, and stress may also affect hair growth.

 How to prevent hair loss while on testosterone therapy

Testosterone therapy leads to increased availability of DHT. However, the 5-alpha reductase enzyme is responsible for converting testosterone to DHT. Therefore, drugs that hinder this conversion work well to prevent hair loss while on testosterone therapy.

• Finasteride is a 5-alpha-reductase blocker approved by the FDA to treat hair loss. It works by reducing blood and scalp DHT levels by about 70%. Hence, little DHT is available to cause shrinking of the hair follicles (follicular miniaturization). 
• Dutasteride is also a 5-alpha-reductase blocker but has yet to get FDA approval for hair loss treatment. It’s far more potent than Finasteride, blocking up to 98.4% of DHT.[14]  
• Minoxidil, a vasodilator, is also approved for hair loss treatment and is often used in combination with Finasteride.

Additionally, consuming lycopene, a natural DHT blocker found in watermelons, tomatoes, mangoes, and carrots, may help prevent baldness while on testosterone therapy.

 Final words

Testosterone affects hair differently in various parts of the body. While it increases beard and pubic hair growth, it has the opposite effect on scalp hair. Testosterone and its more active product, DHT, bind to hair follicles, causing them to regress and eventually lead to hair loss. 

Both men and women experience androgenetic alopecia. However, this type of baldness is more common in men and can be hereditary.