Hair Loss: The Root Cause of Thinning and Shedding

Understanding the Hair Growth Cycle

One of the most important things to understand about hair loss is that what you see happening today may reflect something that happened in your body months ago.

Each hair follicle moves through a natural growth cycle.

Anagen: The Growth Phase

Anagen is the active phase when the hair follicle is producing new hair. Scalp hairs can remain in this phase for years.

The longer a follicle remains in anagen, the longer the hair has an opportunity to grow.

Hormones can influence this phase. For example, higher estrogen levels during pregnancy can prolong anagen, which is one reason many women notice particularly thick hair during pregnancy. As estrogen declines postpartum or during the menopause transition, the hair-growth cycle can change.

Catagen: The Transition Phase

Catagen is a brief transitional period during which active growth stops and the follicle begins preparing for rest.

Only a small percentage of scalp hairs should normally be in this phase at any given time.

Telogen: The Resting Phase

During telogen, the hair is no longer actively growing but remains within the follicle for a period of time.

This phase is particularly important when we’re talking about sudden or increased shedding. Significant physical or emotional stress can cause more follicles than usual to leave the growth phase and enter the resting phase.

Exogen: The Shedding Phase

Finally, the old hair is released from the follicle and sheds as the follicle prepares for another growth cycle.

This delay explains why hair loss can seem to come out of nowhere.

After a significant stressor or physiological change, increased shedding may not become obvious until approximately two to three months later.

That means when hair loss begins, we don’t just ask:

“What’s happening now?”

We also ask:

“What was happening two, three, or even four months ago?”

An illness, high fever, surgery, significant emotional stress, rapid weight loss, restrictive dieting, postpartum hormonal changes, medication or hormone changes, or another physiological stressor may have occurred months before increased shedding became noticeable.

Not All Hair Loss Is the Same

Determining the pattern and type of hair loss is an important part of figuring out its cause.

Telogen effluvium typically causes increased, diffuse shedding across the scalp. It may occur after a physiological or emotional stressor and often becomes apparent several months after the triggering event.

Female pattern hair loss tends to develop more gradually. You may notice widening of the part, decreased density through the crown or top of the scalp, or a smaller ponytail. Progressive miniaturization of the hair follicles causes individual hairs to become shorter and finer over time.

Other forms of hair loss include alopecia areata, traction alopecia, anagen effluvium, trichotillomania, and several forms of scarring alopecia.

Because some types require specific medical treatment, rapidly progressing hair loss, completely bald patches, scalp inflammation, pain, scaling, or evidence of scarring should be appropriately evaluated.

Why Is My Hair Falling Out?

Hair loss is rarely a one-size-fits-all problem. In many patients, more than one contributing factor may be occurring at the same time.

These are some of the areas the doctors at Sklar Center for Restorative Medicine take into account when evaluating hair thinning and shedding.

1. Hormones: Estrogen, Testosterone and DHT

Hormonal changes are an important consideration, particularly when hair loss develops postpartum, during perimenopause or menopause, or after beginning or changing hormone therapy.

Estrogen

Estrogen influences the hair-growth cycle and helps support the anagen, or active growth, phase.

Pregnancy provides a great example. Rising estrogen can prolong anagen, resulting in thicker hair for many women. After delivery, estrogen levels rapidly fall and many of those hairs eventually transition toward shedding at approximately the same time.

During perimenopause and menopause, declining estrogen can also change the hair-growth environment. Hair may become finer, grow more slowly, or spend less time in its active growth phase.

Testosterone and DHT

Testosterone and dihydrotestosterone (DHT) require a little more explanation because their relationship with scalp hair is different from their effects elsewhere in the body.

Testosterone can be converted by the enzyme 5-alpha reductase into DHT, a more potent androgen. DHT binds strongly to androgen receptors within susceptible scalp hair follicles.

Over time, increased androgen signaling can shorten the anagen growth phase and contribute to follicular miniaturization. Instead of producing the same thick terminal hair with each cycle, the follicle begins producing progressively shorter, finer hairs. Eventually, this can become visible as decreased density, widening of the part, or increased scalp visibility.

Do Testosterone and DHT Have to Be High to Cause Hair Loss?

Not necessarily.

Some women experiencing androgen-related hair loss do have testosterone or other androgen levels that are higher than the normal physiological range. This may occur with conditions associated with androgen excess or, in some cases, when using testosterone or DHEA supplementation.

However, circulating hormone levels are only part of the picture.

A woman can have testosterone levels within the laboratory reference range and still experience androgen-sensitive hair loss. The amount of free testosterone, conversion of testosterone into DHT within the tissues, activity of 5-alpha reductase, genetics, and the sensitivity of the individual hair follicle to androgen signaling can all influence what happens at the scalp.

This is why the doctors at Sklar Center don’t evaluate a testosterone result in isolation. We look at hormone levels in the context of the patient’s baseline, symptoms, medications or hormone therapy, other androgen markers, and pattern and timing of hair loss.

If Testosterone or DHT Is Causing Hair Loss, When Would You Notice It?

This is another place where understanding the hair-growth cycle becomes important.

Hair loss related to increased testosterone or DHT exposure is generally not instantaneous.

DHT acts on susceptible follicles over time, progressively shortening the growth phase and miniaturizing the follicle through subsequent hair cycles. Because of this, someone may begin or increase testosterone or DHEA and not immediately see a change in their hair.

Hair thinning or increased shedding may become apparent weeks to months later, depending on the individual’s hair cycle, degree and duration of androgen exposure, genetics, follicular sensitivity, and other contributing factors.

This timing is important clinically.

If hair loss develops after a hormone change, we look backward at the timeline rather than assuming that only what happened in the last few days or weeks is relevant.

We also consider accompanying signs of increased androgen activity, such as new or worsening acne, increased facial or body hair, oily skin, or other hormonal changes.

At the same time, the presence of hair loss does not automatically mean testosterone or DHT is the cause. Iron deficiency, thyroid dysfunction, stress, illness, weight loss, inadequate protein intake, menopause-related hormonal changes, genetics, and other factors may be contributing simultaneously.

2. Perimenopause and Menopause

Hair changes are particularly common during the menopause transition.

Perimenopause is characterized by fluctuating hormones before the final menstrual period. As women progress toward menopause, estrogen and progesterone ultimately decline. These changes can alter the hair-growth cycle and may also change the relative influence of androgens at the follicle.

Women may begin noticing:

• A widening part
• More visible scalp
• Decreased density around the crown or temples
• A thinner ponytail
• Increased shedding
• Finer individual hairs
• Changes in hair texture
• Increased dryness or breakage

Importantly, not every case of hair loss in a woman in her 40s or 50s should automatically be attributed to menopause.

Iron deficiency, thyroid dysfunction, inadequate protein intake, chronic stress, metabolic changes, medications, autoimmune conditions, genetics, and other factors may be occurring at the same time.

3. Thyroid Function

Both too little and too much thyroid hormone can affect the normal hair-growth cycle.

Thyroid dysfunction often causes more diffuse thinning rather than one isolated area of hair loss.

When hair changes occur alongside fatigue, unexplained weight changes, temperature intolerance, constipation, changes in heart rate, or dry skin, thyroid function becomes an especially important area to evaluate.

4. Iron and Nutrient Deficiencies

Hair is not essential for immediate survival.

When nutrients are limited, the body prioritizes vital organs and physiological functions over growing thick, healthy hair.

Nutrients important for hair health include:

• Iron
• Vitamin D
• Vitamin B12 and other B vitamins
• Zinc
• Selenium
• Vitamin C
• Adequate amino acids and protein

Iron deserves particular attention. Someone can have depleted iron stores even before developing overt anemia, which is why evaluating ferritin in addition to a complete blood count and other iron markers may provide valuable information.

Heavy or prolonged menstrual bleeding during the reproductive and perimenopausal years can be one contributor to depleted iron stores.

What About Biotin?

Biotin has become almost synonymous with hair supplements, but more isn’t necessarily better.

Biotin supplementation is most likely to be helpful when someone is actually deficient. Rather than automatically reaching for a high-dose biotin supplement, we prefer to determine which nutrients, if any, actually need support.

5. Not Eating Enough Protein

Hair is largely composed of keratin, a protein, making adequate protein and amino acids essential for hair production.

Restrictive dieting, significant calorie reduction, rapid weight loss, poor appetite, or simply not consuming adequate protein can contribute to increased shedding in susceptible individuals.

This is particularly important during active weight loss, including for patients using medications that significantly decrease appetite.

6. Stress and Cortisol

Stress affects far more than how we feel mentally.

Acute and chronic stress can influence the hair follicle and its growth cycle. A significant stressor may cause more hairs than usual to transition out of the growth phase and eventually into the shedding phase.

And remember the delay:

The stressful event may occur today, while the increased shedding doesn’t become obvious until several months later.

This is why creating a health timeline can be so helpful when investigating hair loss.

7. Blood Sugar, Insulin, and Metabolic Health

Hair follicles also respond to the metabolic environment around them.

Insulin and insulin-like growth factor interact with androgen signaling and may influence 5-alpha reductase activity and androgen pathways.

Metabolic health may therefore be another piece of the puzzle, particularly when hair changes occur alongside insulin resistance, polycystic metabolic ovarian syndrome (PMOS, formerly PCOS), changes in body composition, or other signs of androgen excess.

8. Illness, Inflammation, Surgery, Medications, and Weight Loss

Sometimes the trigger for hair loss isn’t chronic—it is a significant event.

Hair shedding may follow:

• A significant infection or illness
• High fever
• Surgery
• Major physical trauma
• Rapid weight loss
• Significant psychological stress
• Restrictive dieting
• Starting, stopping, or changing certain medications
• Changes in hormone therapy

Because of the hair-growth cycle, shedding may occur well after the initial event has resolved.

Getting to the Root Cause: What Do We Evaluate?

There isn’t one universal “hair-loss panel.”

At Sklar Center, evaluation begins with the story and timeline.

When did the shedding begin? Is it sudden or gradual? Is hair coming out diffusely or only in certain areas? What was happening two to four months before it started? Is there a family history of thinning? Have menstrual cycles changed? Was there a pregnancy, illness, surgery, medication or hormone change, major stressor, or significant weight loss?

From there, laboratory testing can be individualized and may include:

• Complete blood count
• Iron and ferritin
• Thyroid markers
• Vitamin D
• Vitamin B12 and other relevant nutrients
• Zinc and other minerals when indicated
• Testosterone and androgen markers
• DHEA-S
• Estradiol
• Progesterone
• Prolactin when indicated
• Metabolic markers such as glucose and insulin

For patients using hormone replacement therapy or androgen supplementation, we also consider when the hair loss began relative to starting or changing therapy, whether hormone levels have moved outside the desired physiological range, and whether other symptoms of increased androgen activity have appeared.

A physical scalp examination, hair-pull testing, trichoscopy, or evaluation by a dermatologist or trichologist may also be appropriate depending on the pattern and severity of hair loss.

 

Supporting Healthy Hair Growth

Once we better understand why hair loss is occurring, treatment becomes much more individualized.

Build the Foundation First

Hair needs adequate resources to grow.

Foundational strategies may include:

Adequate protein. Include meaningful sources of protein throughout the day and avoid prolonged under-eating.

Nutrient-dense foods. Emphasize vegetables, leafy greens, berries, nuts, seeds, legumes, eggs, fish, and other whole-food sources of vitamins, minerals, essential fatty acids, and amino acids.

Correct deficiencies. Iron, vitamin D, B12, zinc, or other nutrients should be supplemented when appropriate rather than assuming everyone needs the same “hair vitamin.”

Support metabolic health. Balanced meals containing protein, fiber, healthy fats, and complex carbohydrates can help support healthy blood-sugar regulation.

Address sleep and stress. Restorative sleep, appropriate movement, breathing exercises, meditation, counseling, and other stress-management strategies can all be part of a comprehensive hair-restoration plan.

Topical and Prescription Options

Sometimes supporting the underlying cause is only part of treatment, and we also want to directly support the follicle.

Minoxidil is one of the most established topical treatments for female and male pattern hair loss. Low-dose oral minoxidil is also used in appropriately selected patients.

Depending on the type of hair loss and individual circumstances, the doctors at Sklar Center for Restorative Medicine may also consider therapies that reduce androgen signaling or DHT activity, including spironolactone, finasteride, or dutasteride.

These treatments aren’t appropriate for everyone. Some uses in women are off-label and require careful consideration of reproductive status, medical history, risks, benefits, and appropriate monitoring.

Botanical and Topical Support

Certain botanical compounds have also been studied for their potential effects on the hair follicle, inflammation, circulation, or 5-alpha reductase activity.

Ingredients of interest include:

• Saw palmetto
• Pumpkin seed
• Green tea/EGCG
• Red clover
• Ginseng
• Rosemary
• Caffeine

These therapies may be useful components of an individualized plan, but “natural” does not automatically mean appropriate for every person. The underlying type and cause of hair loss should still guide treatment.

PRP and Red-Light Therapy

For some patients, regenerative and device-based therapies may also be worth discussing.

Platelet-rich plasma (PRP) uses a concentration of a patient’s own platelets and associated growth factors and may help support follicles that are still viable.

Low-level light therapy (LLLT), or red-light therapy, has also been studied as a treatment for pattern hair loss and may help support cellular activity within the follicle.

Hair Growth Takes Time

Perhaps one of the most important things to understand when treating hair loss is that hair doesn’t respond overnight.

Just as hair loss may appear months after its original trigger, recovery also takes time.

Because follicles must move through their natural growth cycle, reducing shedding and seeing meaningful new growth can take several months.

Early improvement may simply mean noticing less hair accumulating in the shower, on your clothes, or in your brush. Later, you may begin noticing short new hairs, improved density, or a less-visible part.

Taking standardized photographs of your part and hairline every few months can often be more useful than trying to judge progress from day to day.

Conclusion

Hair loss can be frustrating, but it can also provide valuable information about what is happening elsewhere in the body.

Rather than asking only:

“What can I take to make my hair grow?”

We also want to ask:

“Why has my hair-growth cycle changed?”

For one person, the primary issue may be depleted iron stores. For another, it may be thyroid dysfunction. Someone else may be experiencing telogen effluvium several months after an illness, surgery, rapid weight loss, or stressful event.

For a woman in perimenopause or menopause, changing estrogen and androgen activity may be occurring alongside nutrient deficiencies, poor sleep, metabolic changes, or stress. And for someone using testosterone or DHEA, we may need to consider whether androgen exposure and conversion to DHT are contributing to the picture, while remembering that androgen levels are only one part of a much larger evaluation.

Often, several factors overlap.

At Sklar Center for Restorative Medicine, our doctors take all of these pieces into account. We look at your hair-loss pattern and timeline alongside your hormones, thyroid function, nutrient status, metabolic health, stress, lifestyle, medications, hormone therapy, medical history, and other potential contributors to develop an individualized approach.

Because when it comes to hair loss, supporting the follicle is important but getting to the root cause is where we start.