Hair Loss in Men and Women: Causes, Evaluation, and Treatment

Hair loss is a symptom, not a diagnosis. In men and women, thinning may reflect androgenetic pattern loss, telogen effluvium, hormonal change, thyroid disease, nutrient deficiency, rapid weight loss, medications, inflammation, genetics, scalp disease, or more than one process occurring at the same time. The first job is identifying the pattern. Treatment makes more sense after that.

Hair loss has an unusual ability to turn otherwise rational people into supplement collectors, shampoo detectives, hormone theorists, and late-night researchers.

That is understandable. Hair loss is visible, emotionally difficult, and often frustratingly slow. Someone may notice a widening part, a smaller ponytail, more hair in the shower, recession around the temples, thinning at the crown, or an abrupt increase in shedding without knowing whether the change is temporary or progressive.

The internet does not make this easier. One explanation blames DHT. Another blames menopause. Another says ferritin must be above a particular number. Another promises that red light, biotin, collagen, rosemary oil, or a proprietary supplement will restart the follicle.

Some of those subjects are clinically relevant. None explains all hair loss.

At HormoneSynergy®, we approach hair loss by first asking what type of loss appears to be occurring, what changed before it began, and what other physiology may be contributing. Hormones matter. So do genetics, thyroid function, nutrition, medications, weight loss, stress, scalp health, and age. The relative importance of each is different from one person to the next.

For the broader clinical model, visit the HormoneSynergy® Longevity Medicine Resource Center.

The first question is what kind of hair loss is occurring

“Hair loss” covers several different biological processes. They do not all look the same and they should not all be treated the same way.

Pattern	What it may look like	Common considerations
Androgenetic or pattern hair loss	Progressive recession, crown thinning, widening part, reduced density	Genetics, follicular androgen sensitivity, age, hormonal context
Telogen effluvium	Diffuse increase in shedding, often appearing relatively suddenly	Illness, surgery, major stress, rapid weight loss, under-eating, medications, hormonal change
Alopecia areata	Well-defined patches of hair loss, sometimes affecting brows or other body hair	Autoimmune disease requiring specific evaluation and treatment
Scarring alopecia	Hair loss with inflammation, scalp symptoms, loss of follicular openings or scar-like change	Inflammatory disorders that can permanently damage follicles
Traction or mechanical loss	Breakage or loss in areas exposed to repeated tension	Hairstyles, extensions, repeated pulling or mechanical stress

These categories can overlap. A stressful event can cause telogen effluvium in someone who already has early androgenetic alopecia, making a previously subtle pattern suddenly much more obvious. Menopause can coincide with pattern loss, thyroid changes, iron depletion, dieting, or several years of accumulated follicular miniaturization.

Calling all of that “hormonal hair loss” misses too much.

Androgenetic alopecia: DHT matters, but sensitivity matters too

Androgenetic alopecia is the most common form of progressive pattern hair loss. In genetically susceptible follicles, androgen signaling contributes to progressive miniaturization. Terminal hairs gradually become shorter, finer, and less visible.

Dihydrotestosterone, or DHT, is particularly important in male-pattern hair loss. DHT is produced from testosterone by the enzyme 5-alpha-reductase and binds to androgen receptors within susceptible follicles.

The important word is susceptible. DHT circulates in people who never become bald. Genetics, androgen-receptor biology, local follicular metabolism, age, and other factors help determine how a follicle responds.

In men, androgenetic alopecia commonly produces frontal recession, temple loss, or crown thinning. Women more often develop reduced density through the central scalp or a progressively widening part. The role of androgens in female-pattern hair loss is more complicated, and many women with pattern loss do not have abnormally high circulating testosterone or DHT.

For a deeper explanation, see DHT and Hair Loss: What Actually Drives Follicle Miniaturization.

Female hair loss is not simply a testosterone problem

Hair thinning becomes more common with age and is frequently noticed during perimenopause and menopause. Changes in ovarian hormone signaling may alter the environment in which the follicle operates, but menopause does not create one uniform type of hair loss.

A woman can develop female-pattern hair loss with normal androgen levels. She can develop telogen effluvium during a period of hormonal transition. She may also have thyroid dysfunction, iron deficiency, major stress, rapid weight loss, medication changes, or inflammatory scalp disease at the same time.

Hormone replacement therapy should therefore not be presented as a general treatment for female-pattern hair loss. Hormones should be evaluated and treated for appropriate clinical indications, with hair changes interpreted as one part of the larger picture.

Similarly, testosterone therapy does not automatically cause hair loss. In someone with genetically susceptible follicles, however, androgen exposure and conversion to DHT may become clinically relevant. Dose, serum levels, symptoms, timing, genetics, and the pattern of hair loss all matter.

See Female Hair Loss and Hormones: A Clinical Perspective and Hormone Transitions and Longevity Medicine.

Telogen effluvium: when shedding follows a physiologic disruption

Telogen effluvium behaves differently from pattern hair loss. A larger-than-usual number of follicles move from active growth into the resting phase, followed later by increased shedding.

The delay matters. Hair may begin shedding weeks or months after the event that triggered it. By then, the illness, surgery, emotional event, diet, medication change, or period of rapid weight loss may feel unrelated.

Common triggers include:

Major illness or fever
Surgery or hospitalization
Pregnancy and postpartum hormonal change
Rapid weight loss
Significant calorie restriction or inadequate protein intake
Iron deficiency and other nutritional problems
Major emotional or physiologic stress
Thyroid dysfunction
Medication changes

Telogen effluvium is often reversible once the trigger has resolved, but recovery is slow because the follicle has to move back through its normal growth cycle. It can also expose underlying androgenetic alopecia that had previously gone unnoticed.

GLP-1 medications, rapid weight loss, and hair shedding

Hair loss is now being reported in some people using GLP-1 and GIP/GLP-1 medications, including semaglutide and tirzepatide. The important question is why.

Current evidence does not establish a simple direct toxic effect of these medications on the hair follicle. A 2026 systematic review found an emerging association between several GLP-1 therapies and reported hair loss, with telogen effluvium and androgenetic alopecia among the patterns identified when the type of hair loss was specified. Rapid weight loss was one of the plausible contributors, particularly for telogen effluvium.

That fits with what has long been known about hair physiology. Large changes in body weight, inadequate calorie intake, insufficient protein, depleted iron stores, illness, and other metabolic stressors can all alter the hair cycle.

This does not mean people should avoid appropriate obesity treatment because of fear of hair loss. It does mean that preserving adequate nutrition, protein intake, lean tissue, and a reasonable rate of weight loss deserves attention rather than treating the scale as the only outcome that matters.

If substantial shedding develops during weight-loss treatment, the medication is only one part of the history. The amount and speed of weight loss, dietary intake, iron status, thyroid function, hormonal context, recent illness, and pre-existing pattern loss may all need to be considered.

Iron, ferritin, zinc, vitamin D, and protein

Nutrient status matters, but hair-loss nutrition has become an area where reasonable physiology is frequently turned into unreasonable certainty.

Iron deficiency can contribute to diffuse shedding. Ferritin is useful because it reflects stored iron, but there is no universally established ferritin number that guarantees hair regrowth. Ferritin also needs clinical context because inflammation and other conditions can change its interpretation.

Zinc deficiency can cause hair abnormalities, but more zinc is not automatically better. Excessive long-term zinc intake can impair copper absorption.

Low vitamin D levels are reported more often in several forms of alopecia, but association is not the same as proof that progressively raising vitamin D improves hair growth in people who are already sufficient.

Protein and total energy intake can be particularly important during intentional weight loss. Hair production is not a survival priority. When energy availability drops substantially, the body can reduce resources devoted to active hair growth.

Biotin deserves a mention because it appears in almost every hair supplement. True biotin deficiency can affect hair, but deficiency is uncommon in people eating a varied diet. High-dose biotin can also interfere with several laboratory tests, including some thyroid, hormone, and cardiac assays.

The goal is to correct a deficiency when one exists, not manufacture one from a symptom.

For a more detailed discussion, see Nutrient Deficiencies and Hair Thinning.

Thyroid function belongs in the differential diagnosis

Both hypothyroidism and hyperthyroidism can affect hair growth and shedding. Thyroid-related changes may include diffuse thinning, altered texture, slower growth, or increased shedding, although hair loss by itself is not specific enough to diagnose thyroid disease.

Testing makes the most sense when the history or accompanying symptoms justify it. Fatigue, changes in body weight, temperature intolerance, bowel changes, menstrual changes, heart-rate abnormalities, or a known thyroid history can add context.

Thyroid testing should not become another exercise in finding an explanation for every case of hair loss. Plenty of people with normal thyroid function lose hair for completely different reasons.

Related reading: Thyroid Hormones and Metabolic Health.

When scalp disease changes the conversation

Not every hair-loss problem begins inside the follicle because of hormones or nutrition. The scalp itself may contain the diagnosis.

Persistent redness, scale, pustules, significant itching, pain, burning, tenderness, smooth scar-like areas, loss of visible follicular openings, or rapidly expanding patches deserve dermatologic evaluation.

This is particularly important with scarring alopecias. In these disorders, inflammation can permanently destroy follicles. Early diagnosis matters because the treatment goal may be to stop additional loss rather than regenerate follicles that have already been destroyed.

Alopecia areata also requires a different treatment framework. It is an autoimmune form of hair loss and should not be treated as a nutrient deficiency, DHT problem, or generic manifestation of stress.

What testing may be useful?

There is no single universal laboratory panel for hair loss. Testing should follow the pattern, history, medications, diet, age, sex, rate of loss, associated symptoms, and physical findings.

Depending on the situation, an evaluation may consider:

CBC
Ferritin and broader iron studies when iron depletion is plausible
Thyroid testing
Vitamin D when deficiency risk is present
Zinc or other nutrient testing in selected cases
Hormone evaluation when symptoms, life stage, treatment history, or signs of androgen excess make it relevant
Medication and supplement review
Dietary intake, protein intake, recent weight change, and rate of weight loss

Androgen testing is not required for every woman with female-pattern hair loss. Many affected women have normal circulating androgen levels. Testing becomes more informative when hair loss occurs with findings such as significant acne, hirsutism, irregular cycles, virilization, or another reason to suspect androgen excess.

The scalp examination may provide more information than another tube of blood. When the diagnosis remains unclear, dermatology evaluation, trichoscopy, or occasionally scalp biopsy may be appropriate.

Hair-loss treatment should match the diagnosis

The best-supported treatment for one type of hair loss may be irrelevant to another. Correcting iron deficiency can help someone whose shedding is related to depleted iron stores, but it will not stop genetically driven follicular miniaturization simply because ferritin rises. Finasteride can address androgen signaling in appropriate patients, but it is not a treatment for alopecia areata. Red light may help androgenetic alopecia, but evidence cannot be generalized to every form of shedding.

Minoxidil

Topical minoxidil remains one of the best-established treatments for androgenetic hair loss. It is FDA approved for male and female pattern hair loss in appropriate formulations and can help prolong the growth phase and improve hair density in responders.

Results take time. Initial shedding can occur, and a fair assessment usually requires months rather than weeks. Benefits generally require continued use.

Low-dose oral minoxidil is increasingly used off-label for selected patients who cannot tolerate or do not respond adequately to topical treatment. It is a systemic medication and should not be confused with a stronger version of a cosmetic treatment. Blood pressure effects, fluid retention, increased body or facial hair, heart rate, medication interactions, and individual cardiovascular circumstances need to be considered.

Finasteride and other antiandrogen strategies

Finasteride inhibits type II 5-alpha-reductase and reduces conversion of testosterone to DHT. Oral finasteride is FDA approved for male-pattern hair loss in men. Dutasteride inhibits additional 5-alpha-reductase activity and is also used off-label in some hair-loss settings.

Finasteride, dutasteride, and spironolactone may also be considered off-label in selected women, but the evidence, indications, reproductive considerations, contraindications, and risk-benefit discussion differ from those in men.

Topical finasteride and other topical antiandrogen approaches are also being studied and used clinically. Early evidence is encouraging, but they should not be presented as equivalent to long-established FDA-approved therapies.

Low-level light and laser therapy

Low-level laser or LED therapy has accumulated meaningful evidence for androgenetic alopecia. A 2025 systematic review and meta-analysis including 38 studies found increased hair density compared with placebo in androgenetic alopecia.

That makes red-light and low-level laser devices reasonable options for some people with pattern loss, particularly when used consistently and with realistic expectations.

The evidence is much thinner for other types of alopecia. A device shown to help androgenetic alopecia should not automatically be marketed as a treatment for telogen effluvium, autoimmune alopecia, or scarring disease.

Platelet-rich plasma and procedures

Platelet-rich plasma, microneedling, and other procedural approaches are also used for androgenetic alopecia. Research suggests potential benefit, but protocols vary considerably and evidence is less standardized than it is for established medical treatments such as minoxidil.

Hair transplantation can be highly effective for appropriately selected patients with stable pattern loss and an adequate donor area. It does not correct the biology affecting non-transplanted susceptible follicles, so long-term medical management may still matter.

Inflammatory scalp treatment

Topical corticosteroids and other anti-inflammatory medications can be important when inflammatory scalp disease is present. They are not generic hair-growth agents. The indication is the inflammatory diagnosis.

Earlier treatment matters most with progressive pattern loss

Androgenetic alopecia involves gradual follicular miniaturization. A follicle producing a thinner hair is generally a more realistic treatment target than a follicle that has been severely miniaturized for many years.

That does not mean everyone needs medication at the first sign of shedding. It means persistent patterned thinning deserves a diagnosis rather than years of experimenting with shampoos and supplements while density continues to decline.

Female-pattern hair loss is progressive in many women, and dermatology guidance emphasizes earlier treatment because maintaining existing density is often easier than recovering advanced loss.

Where longevity medicine fits

There is a useful role for longevity medicine in hair loss, but it should not be overstated.

Hair is not a validated longevity biomarker, and thicker hair does not mean someone is biologically younger. At the same time, hair can reveal changes worth investigating. Iron deficiency, thyroid disease, severe calorie restriction, rapid weight loss, hormonal transitions, medication effects, chronic illness, and metabolic stress can first become noticeable through changes in shedding or density.

A broader medical evaluation is especially useful when hair loss appears alongside fatigue, menstrual changes, menopausal symptoms, unexplained weight change, loss of lean mass, rapid weight loss, thyroid symptoms, nutritional restriction, or other systemic changes.

The point is not to force every hair problem into a longevity explanation. It is to avoid missing relevant physiology while the person is being handed another hair supplement.

When nutrient support makes sense

When laboratory testing, dietary history, or clinical circumstances identify a genuine nutritional problem, targeted replacement may be appropriate. Iron, zinc, vitamin D, and protein each have legitimate roles in normal physiology, but none is a universal hair-growth treatment.

For a closer look at the difference between correcting deficiencies and simply taking more supplements, see:

HormoneSynergy® Resource: Browse our Supplement Collection. Nutritional products are best used to address an identified need or support a broader clinical plan, not as substitutes for diagnosing progressive or unexplained hair loss.

When to see a dermatologist promptly

Some patterns deserve dermatology evaluation rather than a prolonged trial-and-error approach. These include:

Rapidly progressive or unexplained hair loss
Smooth, discrete patches of complete hair loss
Scalp pain, burning, marked itching, pustules, or persistent inflammation
Areas that look scarred or where follicular openings are disappearing
Loss involving eyebrows or eyelashes without a clear explanation
Hair loss accompanied by significant systemic symptoms
A diagnosis that remains unclear despite an initial evaluation

Scarring alopecia is particularly important because delay can mean irreversible follicular destruction.

Related Hair Loss Resources

Selected Evidence

Frequently Asked Questions

Is hair loss always hormonal?

No. Hormones can contribute to hair loss, but genetics, telogen effluvium, thyroid disease, nutrient deficiency, rapid weight loss, medications, autoimmune disease, scalp inflammation, and mechanical factors can also cause or contribute to thinning.

Does high DHT always cause hair loss?

No. DHT is important in androgenetic alopecia, particularly in men, but follicular genetic susceptibility is critical. Many people have normal DHT exposure without developing significant pattern hair loss.

Can menopause cause hair thinning?

Hair thinning becomes more common during and after the menopausal transition, and changing hormone signaling may contribute. Menopause does not produce one single form of hair loss, however, and other causes such as female-pattern hair loss, thyroid disease, iron deficiency, stress, or nutritional changes may coexist.

Can low ferritin cause hair loss?

Iron deficiency and depleted iron stores can contribute to diffuse shedding in some people. Ferritin is useful for assessing stored iron, but there is no universally established ferritin target that guarantees hair regrowth.

Can semaglutide or tirzepatide cause hair loss?

Hair loss has been reported with GLP-1-based weight-loss therapies, and recent research suggests an association, particularly with semaglutide and tirzepatide. Rapid weight loss, reduced calorie and protein intake, nutritional changes, and telogen effluvium may contribute. Current evidence has not established one simple direct mechanism in every case.

Does red light therapy work for hair loss?

Low-level laser and LED therapy has evidence for improving hair density in androgenetic alopecia. Evidence is much less established for other forms of hair loss, so the diagnosis matters.

What is the best treatment for female-pattern hair loss?

Topical minoxidil remains the best-established first-line medication for female-pattern hair loss. Other treatments, including spironolactone, low-dose oral minoxidil, finasteride, dutasteride, low-level light therapy, platelet-rich plasma, and combination approaches may be considered in selected patients, often off-label and with different levels of supporting evidence.

What is the best treatment for male-pattern hair loss?

FDA-approved medical treatments include topical minoxidil and oral finasteride. Other approaches, including low-level light therapy, dutasteride, oral minoxidil, procedures, and hair transplantation may be considered depending on the individual and the extent of hair loss.

How long does hair treatment take to work?

Hair grows slowly. Most medical therapies require several months before meaningful change can be judged, and six to twelve months is often a more realistic assessment period for pattern hair loss. Continued treatment is usually required to maintain benefits from therapies such as minoxidil or antiandrogen treatment.

When should hair loss be evaluated by a dermatologist?

Dermatology evaluation is particularly important when hair loss is rapid, patchy, painful, inflamed, associated with scalp burning or scarring, involves loss of follicular openings, or remains diagnostically unclear. These findings can indicate conditions that require specific treatment.