5-alpha-reductase, DHT & the hair trade-off

What actually decides this outcome, in order of size

The same enzyme product is wanted in one tissue and unwanted in another, in the same person, at the same time. Nothing on this page escapes that. Ranked by how much of the outcome each factor owns:

1. Genetics, which decides whether follicles are androgen-sensitive at all. Androgenetic alopecia is a follicular sensitivity pattern rather than a DHT excess; men with identical serum DHT differ completely in outcome. This is the largest determinant on the page and it is not for sale.
2. How early the intervention starts, because the two halves of the problem are not equally reversible. Miniaturized follicles can be restored; scarred and absent ones cannot. Relative efficacy of the available agents has been compared directly Gupta 2022, and every one of those numbers is a number about preservation more than regrowth.
3. WHICH ISOENZYME, which decides both the benefit and the price. Finasteride inhibits type 2; dutasteride inhibits types 1 and 2 and suppresses serum DHT far more completely Roehrborn 2002, with a half-life measured in weeks rather than hours Steiner 1996. Deeper and longer suppression is a stronger hair drug and a stronger everything-else drug, and the comparison has been made in regrowth terms Gupta 2022.
4. What the suppression costs, stated as a measured quantity rather than a rumor. Sexual, physical and overall adverse effects under 5-alpha-reductase inhibition have been pooled in a systematic review and meta-analysis Zhang 2022, and the depression and suicide question has been examined specifically Gupta 2025. The prescribing information is the primary document for what is on the label Propecia label 2022. That is the honest way to hold this: a real probability, in a minority, for a real cosmetic benefit.
5. The prostate, where the sign is the other way round. A randomized trial of dutasteride reported on prostate cancer risk Andriole 2010, and a companion analysis reported on what the drug does to the usefulness of prostate specific antigen as a test Andriole 2011. That second one is not a side effect. It is a permanent change to the interpretation of a measurement.
6. Whether the route can be kept local, which is the entire argument for the topical half. RU58841 was designed as a topical antiandrogen intended to act in skin without systemic androgen blockade Battmann 1994, and Ketoconazole Shampoo has long-term use data in androgenetic alopecia Pierard-Franchimont 1998. Local action is a plausible way to buy one sign without the other, and it is a design intention rather than a demonstrated separation in humans.

The order to run these in, and what has to be true first

Decide what you are willing to pay before you start, because the two sides of this enzyme are not separable by wishing. Then start with the agent that does not touch it at all.

1. Rule out the losses that are not androgenic first. Ferritin, TSH (Thyroid-Stimulating Hormone) with Free T4 (Thyroxine), and a look at recent illness, weight change and medication. Diffuse shedding from iron or thyroid status is common, it is treatable, and no drug on this page addresses it.
2. Minoxidil before any hormonal step, because it does not touch the axis. It is a vasodilator prodrug requiring follicular sulfotransferase activation, and that enzyme activity has been studied as a predictor of who responds Pietrauszka 2022. The oral low-dose route has a multicenter safety series behind it Vano-Galvan 2021 and is a systemic cardiovascular drug being used for a cosmetic endpoint, which is a real decision rather than a formality.
3. Ketoconazole Shampoo is the cheapest adjunct with a topical rationale Pierard-Franchimont 1998. Small effect, negligible systemic exposure, and no reason not to run it alongside.
4. Finasteride is the first systemic step and the label is the document to read first Propecia label 2022. Type 2 inhibition, partial serum DHT suppression, and the adverse-effect literature summarized rather than anecdotal Zhang 2022 Gupta 2025.
5. Dutasteride is the escalation and should be treated as one. Dual isoenzyme inhibition Roehrborn 2002 with a long half-life Steiner 1996 means a decision to stop takes weeks to express itself. Better hair evidence Gupta 2022, deeper suppression, slower exit.
6. Baseline PSA (Total + Free + % Free) before any 5-alpha-reductase inhibitor if you are over forty, and this is the step nobody does. The effect of the drug on the usefulness of the test is documented Andriole 2011, and assay standardization already introduces its own differences between laboratories Jansen 2008. A pre-treatment value is what makes later results readable.
7. RU58841 is the topical-only strategy and it is unapproved. The design intent was skin-local antiandrogen action Battmann 1994. There is no human program establishing that the separation holds at the doses people actually apply, and saying so is the entry.
8. Saw Palmetto, Nettle Root, Beta-Sitosterol, Pygeum, Pumpkin Seed Oil and Zinc are the botanical shelf and they are a urinary-symptom literature. The dose-ranging trial of saw palmetto extract for lower urinary tract symptoms is the most informative single document here Barry 2011, and it is not a hair trial.

What gets bought for this that cannot move it

The category that fails structurally is the botanical 5-alpha-reductase inhibitor bought for hair. The plant extracts on this page were investigated for prostatic symptoms, and the most informative trial escalated the dose of saw palmetto extract and reported the result on urinary symptoms Barry 2011. Even taken at face value, a urinary-symptom endpoint is not a follicular one: hair requires sustained suppression at the follicle over months, which is a much harder pharmacological ask than a symptom score. Buying the botanical because it is the gentle version of finasteride is buying a different drug for a different organ.

The direction problem is the whole page and it cannot be engineered away orally. DHT drives follicular miniaturization and prostate growth, and it also supports libido and erectile function in many men. A systemic inhibitor cannot choose a tissue. The pooled adverse-effect data is the honest quantity Zhang 2022, the mood question has been looked at directly Gupta 2025, and the correct reading is a real risk in a minority rather than either a certainty or a myth. A reader who is told there is no cost will stop the drug at the first bad week and never find out whether it worked.

The failure that shows up decades later is the test. These drugs lower prostate specific antigen substantially, and the effect on the test's usefulness has been analyzed Andriole 2011. Somebody who starts at thirty-two for hair and is screened at fifty-eight without anyone knowing they are on it is being interpreted against the wrong reference. Assay differences between laboratories already exist Jansen 2008; this adds a systematic one on top. Tell whoever orders the test, every time, and keep the pre-treatment number.

If the goal underneath is different, so is the page. If the concern is follicle biology rather than the enzyme, Hair — follicle biology & the androgen problem. If libido is the actual complaint, Hormonal substrate — testosterone, estrogen, prolactin, thyroid. If the hair loss is patchy rather than patterned, or is shedding rather than thinning, that is a dermatology assessment and not this page. And persistent low mood after starting any agent here is a reason to speak to a doctor rather than to push through.

How you would know it was working, on a real read-out and a real timescale

This page makes two predictions. PSA (Total + Free + % Free) will fall substantially on any 5-alpha-reductase inhibitor and that fall is an artifact of the drug rather than an improvement Andriole 2011; and hair will not visibly change inside six months on anything here, because the follicular cycle sets the timescale rather than the pharmacology does.

• PSA (Total + Free + % Free) at baseline before the first dose, then annually from forty. This is the single most useful measurement on the page and it has to be drawn first, because after treatment starts there is no way to reconstruct it Andriole 2011 Jansen 2008.
• Total & Free DHT with Total Testosterone, Free Testosterone and SHBG (Sex Hormone-Binding Globulin) at baseline and twelve weeks. Twelve weeks because suppression is established within days and the twelve-week draw is really asking what the rest of the axis did in response; dutasteride's long half-life means its numbers are still moving at week four Steiner 1996.
• Ferritin and TSH (Thyroid-Stimulating Hormone) once at the start. The two reversible causes of hair loss that get treated as androgenetic, and the only two on this list with a cheap fix.
• Standardized photographs, same light, same part, same distance, at baseline and at six and twelve months. Six months is the earliest honest look because the anagen fraction takes that long to re-express, and the comparative efficacy literature is reported over that kind of window Gupta 2022. Memory is not a read-out here; photographs are.
• A written note of libido, erectile function and mood, scored the same way monthly for the first six months. The adverse-effect literature is about a minority Zhang 2022 Gupta 2025, and a score kept prospectively is the only way to know which side of it you are on rather than deciding retrospectively.

What will fool you. Shedding in the first two months on Minoxidil is a synchronization effect rather than a failure. Non-response to minoxidil may be a sulfotransferase phenotype rather than a dosing problem Pietrauszka 2022, which is a testable idea and not yet a routine test. A low PSA (Total + Free + % Free) on treatment is reassuring only if it is being compared against the right expectation Andriole 2011. RU58841 applied topically has no human program establishing that systemic exposure stays negligible at real-world doses Battmann 1994, so a normal Total & Free DHT on it is not proof of local action. And stopping dutasteride does not stop the drug for weeks Steiner 1996, so an early conclusion after quitting is about the wrong time window.

Sources read for these sections

• Zhang JJ, et al. Sexual, physical, and overall adverse effects in patients treated with 5alpha-reductase inhibitors: a systematic review and meta-analysis. Asian Journal of Andrology 2022 · PMID 34747724
• Gupta AK. Finasteride Use: Evaluation of Depression and Suicide Risk. Journal of Cosmetic Dermatology 2025 · PMID 40082195
• Andriole GL, Bostwick DG, Brawley OW. Effect of dutasteride on the risk of prostate cancer.. N Engl J Med 2010 · PMID 20357281
• Andriole GL, Bostwick D, Brawley OW. The effect of dutasteride on the usefulness of prostate specific antigen for the diagnosis of high grade and clinically relevant prostate cancer in men with a previous negative biopsy: results from the REDUCE study.. J Urol 2011 · PMID 21074214
• Roehrborn CG, Boyle P, Nickel JC. Efficacy and safety of a dual inhibitor of 5-alpha-reductase types 1 and 2 (dutasteride) in men with benign prostatic hyperplasia.. Urology 2002 · PMID 12350480
• Steiner JF. Clinical pharmacokinetics and pharmacodynamics of finasteride.. Clin Pharmacokinet 1996 · PMID 8846625
• Gupta AK. Relative Efficacy of Minoxidil and the 5-alpha Reductase Inhibitors in Androgenetic Alopecia Treatment of Male Patients: A Network Meta-analysis. JAMA Dermatology 2022;158(3):266-274 · PMID 35107565
• Barry MJ, et al. Effect of increasing doses of saw palmetto extract on lower urinary tract symptoms: a randomized trial. JAMA, 2011 · PMID 21954478
• Battmann T, Bonfils A, Branche C. RU 58841, a new specific topical antiandrogen: a candidate of choice for the treatment of acne, androgenetic alopecia and hirsutism.. J Steroid Biochem Mol Biol 1994 · PMID 8136306
• Pierard-Franchimont C. Ketoconazole shampoo: effect of long-term use in androgenic alopecia.. Dermatology 1998 · PMID 9669136
• Vano-Galvan S, et al. Safety of low-dose oral minoxidil for hair loss: A multicenter study of 1404 patients. Journal of the American Academy of Dermatology 2021 · PMID 33639244
• Pietrauszka K, Bergler-Czop B. Sulfotransferase SULT1A1 activity in hair follicle, a prognostic marker of response to the minoxidil treatment in patients with androgenetic alopecia: a review. Postepy Dermatologii i Alergologii 2022 · PMID 35950120
• U.S. Food and Drug Administration. PROPECIA (finasteride) tablets, 1 mg — full prescribing information, including the twelve-month adverse experience table and the postmarketing report of persistent sexual dysfunction. DailyMed, U.S. National Library of Medicine; label revised 2022
• Jansen FH, et al. Clinical impact of new prostate-specific antigen WHO standardization on biopsy rates and cancer detection. Clinical Chemistry 2008 · PMID 18927249