Androgenetic Alopecia

What androgenetic alopecia is

Androgenetic alopecia is a heritable, androgen-dependent, progressive miniaturisation of scalp hair follicles that follows a pattern. Each word in that sentence is doing work. Heritable is why the labels ask about family history. Androgen-dependent is why the only oral drug approved for it is a 5α-reductase inhibitor. Progressive is why a five-year placebo arm ends with every untreated man having lost hair from baseline. And the pattern is why it is separable from the alopecias that are diffuse or patchy.

Miniaturisation is the mechanism and it is worth understanding, because it explains why treatment protects more than it restores. Affected follicles do not die at once; they cycle back each time thinner, shorter and lighter, until what grows from them is barely visible and eventually nothing does. Reversing a miniaturised follicle is possible while it is still cycling. Once the follicle is gone, no drug on any label brings it back — which makes the timing of the decision the most consequential thing about it.

It is common enough that the European treatment guideline describes it as "the most common hair loss disorder, affecting both men and women" and states that its frequency "increases with age and affects up to 80% Caucasian men and 42% of women". Read the qualifier: that is a lifetime figure for one ancestry group, quoted from a guideline, and it is not a statement about your decade.

One thing it is not: a hormone problem. This is the commonest inference men make and it is wrong in both directions. Androgenetic alopecia occurs at entirely normal testosterone levels, and a low testosterone does not produce it — our hypogonadism page states, quoting the Endocrine Society’s own list of specific signs, that loss of established body hair is a different observation from male pattern baldness and that androgenetic alopecia is not a sign of hypogonadism. Nothing on this page should be read as a reason to have your testosterone measured.

Why the pattern is not the proof

Almost everything a man can observe about his own hair loss is shared with the conditions this diagnosis has to be separated from. Thinning is shared with telogen effluvium. Increased shedding is shared with telogen effluvium and with several drug effects. A visible scalp is shared with essentially everything. The one observation that genuinely favours androgenetic alopecia — the pattern — is also the one most easily misread, because a diffuse process superimposed on early pattern loss looks like advanced pattern loss.

The structured signs at the foot of this section are short for a reason that is worth stating plainly rather than hiding. This condition has very few findings a clinician can make that a man cannot see in a mirror. That is not a gap in our sourcing; it is why the diagnosis is made by exclusion. The clinician’s advantage is not a secret sign — it is a dermatoscope, a hair count, and a differential list they can actually run.

What a clinician does that a mirror does not: look at whether the follicular openings are still present, because their loss means scarring and scarring means permanence; look at whether hairs in one small area vary in calibre, which is what miniaturisation looks like under magnification; count hairs in a defined area rather than estimating; and check for scale, redness, pustules or pain, because an inflamed scalp is the label’s own reason to stop and see someone.

The most useful thing a man can bring to that appointment is not a self-assessment. It is a timeline — when it started, whether it was sudden, whether anything happened three to four months before it started, what medications changed — and a photograph from several years ago. The history discriminates in a way the current appearance does not.

The signs that are specific — and none of them are self-assessable

A hair count in a defined area of scalp

The endpoint the pivotal finasteride trials used, and a measurement rather than an impression: hair counts were assessed by photographic enlargements of a representative area of active hair loss, in a one-inch diameter circle of 5.1 cm². Nobody estimates this accurately by eye, including the man whose scalp it is.

The proportion of hairs in the growing phase

Measured by phototrichogram in a 1 cm² target area. The PROPECIA label reports the proportion of anagen hairs improving from 62% at baseline to 68% on treatment over 48 weeks — a real change, invisible to inspection, and the kind of figure that shows how small the differences being measured are.

A stage assigned against the Hamilton–Norwood classification by an examiner

Norwood published the classification in 1975 alongside incidence data from 1,000 white adult male subjects, and developed it because "the success of hair transplant surgery is largely dependent on proper patient selection". It was built to select surgical candidates, not to make a diagnosis, and it describes a scalp now rather than predicting one later.

The diagnostic criteria, quoted

Each criterion below is the guideline’s own wording, not a summary of it. Our reading follows underneath, so you can weigh one against the other.

1. The approved indication, and the region it does not cover

   “PROPECIA® is indicated for the treatment of male pattern hair loss (androgenetic alopecia) in MEN ONLY. Efficacy in bitemporal recession has not been established.”

   Two sentences, and the second is the one nobody quotes. Bitemporal recession is the temples, and the temples are the finding most men present with. Note also the capitals in the original: MEN ONLY is the label’s own emphasis, and the label goes further in section 14.2 — in 137 postmenopausal women with androgenetic alopecia, "effectiveness could not be demonstrated".

2. What was measured, and where it stopped

   “Hair counts were obtained in the anterior mid-scalp area, and did not include the area of bitemporal recession or the anterior hairline.”

   This is the sentence that draws the boundary on the front of the scalp. There is a dedicated 12-month study in the anterior mid-scalp, it did show a significant increase in hair count, and it deliberately excluded the hairline and the temples from the count. So the label supports a claim about the middle of the front of your head and supports no claim at all about its edge — a distinction that disappears in every before-and-after photograph you will be shown.

3. The pattern has to match, and the front of the scalp is out

   “your amount of hair loss is different than that shown on the side of this carton or your hair loss is on the front of the scalp. 5% minoxidil topical solution is not intended for frontal baldness or receding hairline.”

   The labelled use of both 5% minoxidil presentations is "to regrow hair on the top of the scalp (vertex only, see pictures on side of carton)". A pattern that does not match the carton is a reason not to self-treat, and the reason is diagnostic rather than cosmetic: a loss that is not in the androgenetic pattern is probably not androgenetic. The foam label carries the identical bullet with the word "foam" in place of "solution".

4. Not sudden, and not patchy

   “your hair loss is sudden and/or patchy”

   Eight words carrying two separate exclusions. Sudden diffuse shedding, typically two to four months after an illness, an operation, a crash diet or a severe stressor, is the picture of telogen effluvium — which is usually self-limiting and needs the cause found rather than a topical. Discrete round patches of complete loss, often with normal skin between them, is the picture of alopecia areata, which is autoimmune and treated entirely differently. Androgenetic alopecia is neither sudden nor patchy; it is slow and patterned.

5. A family history, or a reason you can name

   “you have no family history of hair loss”

   Heritability is part of the definition of the condition, so its absence lowers the prior and raises everything else on the differential. Treat this as a probability statement rather than a rule — a dermatologist can and does diagnose androgenetic alopecia in a man with no family history, on the strength of an examination. The bullet is telling the man in the shop that he cannot.

6. An inflamed scalp is a different problem

   “your scalp is red, inflamed, infected, irritated, or painful”

   The most important bullet on the carton, and the one that maps onto the exclusion with the highest cost of being missed. Androgenetic alopecia does not make a scalp sore, scaly or red. Redness, scale, pustules, burning or tenderness point towards an inflammatory or scarring alopecia, towards tinea capitis, or towards a dermatitis — and in the scarring group the follicle is being destroyed while the topical is being applied.

7. And the state of the diagnostic evidence, stated by the only body that wrote a guideline

   “As evidence-based guidelines on hair disorders are rare, a European consensus group was constituted to develop guidelines for the diagnostic evaluation and treatment of AGA.”

   Worth knowing before anyone quotes "the guidelines" at you. The only diagnostic guideline in this field is graded S1, which in the classification it was written under means expert consensus without a systematic evidence review, and the same abstract describes its content as "expert opinion-based recommendations". Its treatment counterpart from the same forum is graded S3. The asymmetry is real and it is the reason this page leans on labels.

Where the guidelines disagree

On these points there is no consensus to report. Both positions are printed with the wording each body used.

The nearest thing to diagnostic criteria a man is ever handed

The complete "Do not use if" list from the 5% minoxidil Drug Facts label, in label order, with what each bullet is excluding. This is FDA-reviewed text on an over-the-counter carton, and it is a better exclusion list than most articles about hair loss contain.

Reproduced complete, because the value of an exclusion list is destroyed by trimming it. The wording is identical on the 5% solution and the 5% foam except for the product name in the second bullet, where the solution reads "5% minoxidil topical solution is not intended for frontal baldness or receding hairline" and the foam reads "5% minoxidil topical foam is not intended for frontal baldness or receding hairline". Note what the list is not: it is a set of reasons not to self-treat, not a rule for a clinician. A dermatologist may well diagnose androgenetic alopecia in a man with no family history. The point of the list is that you cannot. Sources: [2] [3]

Which part of the scalp each treatment was actually studied on

The two approved drugs do not cover the same head, and neither covers the temples. Every cell comes from the labelled indication or the clinical studies section of the label named in the column.

The temples are the finding men most often present with and the only region both labels explicitly decline. The PROPECIA label states "Efficacy in bitemporal recession has not been established" in its Indications section, and describes the mid-scalp study as one in which "Hair counts were obtained in the anterior mid-scalp area, and did not include the area of bitemporal recession or the anterior hairline". Nothing in either label supports a claim about a receding hairline, and a clinic that makes one is not quoting a label. Sources: [1] [2] [3]

What the pivotal trials measured, and in whom

Before reading any percentage about either drug, read who it was measured in. Both labels state their trial populations, and both populations are narrower than the men being sold to.

Two things to carry away. The finasteride trials stopped at 41 and the minoxidil trials at 49, so neither label speaks to a man of 55 — that is a limit on the evidence, not a statement that the drugs fail. And the largest number on the finasteride row is the placebo one: at five years every untreated man in the trial had lost hair from his own baseline. The comparison being made is with the alternative of doing nothing, in men who had already started losing hair. Sources: [1] [2]

What the guidelines are, and what class of evidence each carries

Three guideline documents exist in this field and none of them is American. The class matters: S1 means expert consensus with no systematic evidence review, S3 means systematic literature review plus formal consensus.

The first two rows are the same forum grading its own work differently on the two halves of the problem, and the gap is the honest state of the field: what to prescribe has been systematically reviewed, how to establish who should get it has not. The last row is a statement about our search rather than a proof of absence — if a United States diagnostic guideline for androgenetic alopecia exists, we did not find it, and this page will be updated if someone points us at one. Sources: [4] [5] [6]

The tests, and what each one answers

The alopecias this has to be separated from

This is the working part of the page, because androgenetic alopecia is what is left when these have been excluded rather than something confirmed on its own. Two of them are urgent in the sense that matters — the follicle is being lost while the wrong treatment is applied. The FDA wrote most of this list into an over-the-counter carton as reasons not to self-treat, which is a fair summary of how confidently a man can run it himself.

Telogen effluvium

Diffuse shedding that starts suddenly, classically two to four months after an illness, an operation, a severe stressor, a crash diet or a new drug, and usually settles once the cause is gone. The minoxidil label excludes exactly this presentation with the bullet "your hair loss is sudden and/or patchy", because the treatment for it is finding the trigger rather than applying a topical to a scalp that is already recovering.

Alopecia areata

Autoimmune, and the other half of the same excluded bullet: discrete patches of complete hair loss, often round, frequently with normal-looking skin between them, sometimes affecting beard or eyebrows too. It can remit spontaneously and it can progress, and it has a treatment pathway of its own that has nothing in common with a 5α-reductase inhibitor.

Scarring (cicatricial) alopecia, including frontal fibrosing alopecia

The one where delay is measured in follicles. The inflammation destroys the follicle permanently, so what is lost does not come back whatever is applied afterwards — and the early presentation of frontal fibrosing alopecia is a receding frontal hairline, which is precisely the picture a man will read as ordinary pattern loss. The label’s exclusion for a scalp that is "red, inflamed, infected, irritated, or painful" is pointing at this group.

Tinea capitis and other scalp infections

A fungal infection of the scalp produces patchy loss with scale and sometimes broken hairs and tenderness, and it needs an oral antifungal rather than anything on this page. It falls under the same Drug Facts exclusion for an inflamed, infected or irritated scalp, and it is a reminder that the carton’s exclusion list is doing real diagnostic work rather than covering a manufacturer legally.

Drug-induced hair loss

A long list including anticoagulants, retinoids, some antihypertensives, chemotherapeutic agents and anabolic steroid use, and the reason the minoxidil label excludes a man who does "not know the reason for your hair loss". This is the differential with the best ratio of effort to result, because the fix is a conversation about a prescription rather than a new one.

Female pattern hair loss, in anyone the male labels exclude

Not a semantic point. Both 5% minoxidil products state "For use by men only" and exclude women in the first Do not use bullet, and the PROPECIA label reports that in 137 postmenopausal women with androgenetic alopecia "effectiveness could not be demonstrated" — no improvement in hair counts, self-assessment, investigator assessment or photographs. The pattern, the workup and the evidence are different.

Hypogonadism — which this is not, in either direction

Listed because it is the inference men most often make. Androgenetic alopecia occurs at normal testosterone concentrations and is not among the specific signs of testosterone deficiency; our hypogonadism page states that androgenetic alopecia is not a sign of hypogonadism, quoting the guideline list it is absent from. Hair loss is not a reason to have a testosterone panel drawn, and a normal testosterone is not a reason to stop investigating hair loss.

What treatment means here

Numbers this page will not give you

Each of these is a figure other pages state confidently. Each is omitted here because no source we could open supports one.

What are the diagnostic criteria for androgenetic alopecia?

No criteria set is printed because none exists in a document we could open. We found no United States diagnostic guideline for this condition at all. The only European one is graded S1 and describes its own content as "expert opinion-based recommendations", while the same forum’s treatment guideline is graded S3 with a systematic literature review behind it. What this page prints instead is the exclusion list from the FDA-reviewed minoxidil Drug Facts label, complete and in label order, which is the nearest thing to formal criteria that exists in American labelling — and it is a list of reasons not to self-diagnose rather than a test.

What percentage of men have hair loss at my age?

No decade-by-decade figure is printed. The one guideline-level number we could source is the European treatment guideline’s statement that androgenetic alopecia "affects up to 80% Caucasian men and 42% of women" — a lifetime upper bound for one ancestry group with no age breakdown and no cohort attached. Norwood’s 1975 paper does report incidence by age, in 1,000 white adult male subjects, in a study designed to select hair transplant candidates. Neither is a current age-specific prevalence and this page will not assemble one from them.

Will treatment bring my hairline back?

Neither label supports a hairline claim and this page will not make one. The PROPECIA label states "Efficacy in bitemporal recession has not been established" in the Indications section itself, and its anterior mid-scalp study excluded the hairline and the temples from the hair counts. Both 5% minoxidil labels state the product "is not intended for frontal baldness or receding hairline". The claim that either drug restores a hairline is made in marketing and is absent from every label we read.

How much hair will I keep if I start treatment now?

No individual prediction is given because none is derivable. The labels report group averages in specific trial populations — a 107-hair difference from placebo at 12 months in a 5.1 cm² circle, rising to 277 hairs at five years — and those are differences between arms in men aged 18 to 41 who all also used a tar-based shampoo for the first two years. Converting a group mean into a forecast for one scalp is not something the data supports, and the label itself says the amount of regrowth "is different for each person".

Should I have my testosterone tested because of hair loss?

Nothing on this page is a reason to. Androgenetic alopecia is androgen-dependent but occurs at entirely normal testosterone concentrations, and it does not appear among the specific signs of testosterone deficiency — our hypogonadism page states, from the Endocrine Society’s own list, that loss of established body hair is a different observation from male pattern baldness and that androgenetic alopecia is not a sign of hypogonadism. Both guidelines on that page also recommend against testing men who have no reason to be tested.

Frequently asked questions

How do I know my hair loss is male pattern baldness and not something else?

You largely cannot, and the FDA says so on the packaging. The 5% minoxidil Drug Facts carton tells the buyer not to use the product if "you do not know the reason for your hair loss", if "your hair loss is sudden and/or patchy", if "you have no family history of hair loss", or if "your scalp is red, inflamed, infected, irritated, or painful". Those four bullets are pointing at telogen effluvium, alopecia areata, the scarring alopecias and scalp infection respectively. The one with the highest cost of being missed is the scarring group, because the follicle is destroyed permanently and the earliest sign of frontal fibrosing alopecia is a receding hairline — which looks exactly like ordinary pattern loss to anyone without magnification.

Will finasteride or minoxidil regrow my hairline?

No label supports that claim. The PROPECIA label states in its Indications section that "Efficacy in bitemporal recession has not been established", and its dedicated anterior mid-scalp study reports that hair counts "did not include the area of bitemporal recession or the anterior hairline". Both 5% minoxidil labels state the product "is not intended for frontal baldness or receding hairline" and describe the labelled use as the top of the scalp, vertex only. The middle of the front of the scalp is covered by one of the two drugs; the hairline and the temples are covered by neither.

How long before I know whether treatment is working?

Both labels give a figure and they differ. Minoxidil: "Results may occur at 2 months with twice a day usage. For some men, you may need to use this product for at least 4 months before you see results", with an explicit stop-and-ask-a-doctor trigger if there is no regrowth at 4 months. Finasteride: "In general, daily use for three months or more is necessary before benefit is observed", with maximum improvement in hair count achieved during the first two years. The labels also agree on what happens when you stop — finasteride’s says "Withdrawal of treatment leads to reversal of effect within 12 months" and minoxidil’s says continued use is necessary "or hair loss will begin again".

Does hair loss mean my testosterone is low?

No, in both directions. Androgenetic alopecia is androgen-dependent but occurs at completely normal testosterone concentrations, and it is not on the list of specific signs of testosterone deficiency. Our hypogonadism page puts it in terms, working from the Endocrine Society’s own list: loss of established axillary and pubic hair is a different observation from male pattern baldness, and androgenetic alopecia is not a sign of hypogonadism. Both guidelines on that page recommend against measuring testosterone in men with no reason to be tested, and hair loss is not a reason.

Are the trial results relevant to a man in his fifties?

Not directly, and this is the population caveat most often dropped. The finasteride trials enrolled "men (88% Caucasian) with mild to moderate androgenetic alopecia (male pattern hair loss) between 18 and 41 years of age", and the 5% minoxidil label describes its studies as being in "mostly white men aged 18-49 years with moderate degrees of hair loss". Neither says anything about a man of 55, and neither enrolled complete hair loss — the finasteride studies specify "mild to moderate, but not complete, hair loss". That is a limit on what the evidence covers rather than a finding that the drugs stop working.

Is dutasteride better than finasteride for hair loss?

Two national positions exist and they are not the same. Japan’s 2017 guideline lists "finasteride 1 mg daily, dutasteride 0.5 mg daily and topical 5% minoxidil twice daily" among its first-line treatments for male-pattern hair loss. In the United States, the AVODART label’s Indications section names one indication and it is symptomatic benign prostatic hyperplasia — we read it in full and there is no hair loss indication. So in the US dutasteride for hair is off-label prescribing, which is lawful and common and is a different thing from an approved use. This page does not rank them, because no head-to-head comparison it could quote was opened.

What does finasteride do to a PSA test?

It lowers it, and you have to tell whoever orders the test. The PROPECIA label reports that at 1 mg in men aged 18 to 41, "the mean value of serum prostate specific antigen (PSA) decreased from 0.7 ng/mL at baseline to 0.5 ng/mL at Month 12", and that at the 5 mg dose used for prostate enlargement "PSA levels are decreased by approximately 50%". The label’s instruction is that "Any confirmed increase from the lowest PSA value while on PROPECIA may signal the presence of prostate cancer and should be evaluated, even if PSA levels are still within the normal range for men not taking a 5α-reductase inhibitor". A normal-looking number in a man on finasteride is not the same as a normal number.

Are there guidelines for diagnosing this, and what do they say?

There is one, it is European, and it is graded S1 — the weakest guideline class, meaning expert consensus with no systematic evidence review. Its own abstract explains the situation: "As evidence-based guidelines on hair disorders are rare, a European consensus group was constituted", and it describes its content as "expert opinion-based recommendations for sex-dependent steps in the diagnostic procedure". The same forum’s treatment guideline is graded S3 with a systematic literature review behind it. We found no United States diagnostic guideline for androgenetic alopecia at all, which is why the criteria on this page are quoted from FDA-reviewed drug labels instead.

Sources

1. [1]PROPECIA (finasteride) tablets, 1 mg — FDA prescribing information, Organon LLC, NDA 020788, via DailyMed. Section 1: "PROPECIA® is indicated for the treatment of male pattern hair loss (androgenetic alopecia) in MEN ONLY. Efficacy in bitemporal recession has not been established."
2. [2]Men’s Rogaine Extra Strength Unscented (minoxidil 5% w/v) topical solution — FDA OTC Drug Facts label, Kenvue Brands LLC, NDA 020834, via DailyMed. Contains the complete "Do not use if" exclusion list quoted throughout this page.
3. [3]Men’s Rogaine (minoxidil 5% w/w) topical aerosol foam — FDA OTC Drug Facts label, Kenvue Brands LLC, NDA 021812, via DailyMed. Same labelled use and the same exclusion list as the solution, with the product name changed in the frontal-baldness bullet.
4. [4]Blume-Peytavi U, Blumeyer A, Tosti A, et al. S1 guideline for diagnostic evaluation in androgenetic alopecia in men, women and adolescents. Br J Dermatol. 2011;164(1):5–15. PMID 20795997 — the only diagnostic guideline in this field we could locate, and it is graded S1.
5. [5]Kanti V, Messenger A, Dobos G, et al. Evidence-based (S3) guideline for the treatment of androgenetic alopecia in women and in men — short version. J Eur Acad Dermatol Venereol. 2018;32(1):11–22. PMID 29178529 — "affects up to 80% Caucasian men and 42% of women".
6. [6]Manabe M, Tsuboi R, Itami S, et al. Guidelines for the diagnosis and treatment of male-pattern and female-pattern hair loss, 2017 version. J Dermatol. 2018;45(9):1031–1043. PMID 29863806 — the Japanese Dermatological Association guideline naming four first-line treatments and two that should not be performed.
7. [7]AVODART (dutasteride) soft gelatin capsules — FDA prescribing information, via DailyMed. Read in full for this page: the Indications and Usage section names symptomatic benign prostatic hyperplasia and contains no hair loss indication.
8. [8]Norwood OT. Male pattern baldness: classification and incidence. South Med J. 1975;68(11):1359–1365. PMID 1188424 — the classification paper, based on 1,000 white adult male subjects and written because "the success of hair transplant surgery is largely dependent on proper patient selection".