Testosterone therapy (TRT) can be linked to hair loss, but the direct evidence in men treated for low testosterone is thin. Pattern hair loss is driven by DHT, a hormone the body makes from testosterone, in follicles that are inherited to be sensitive to it. Testosterone labels list hair loss, and in trans men starting testosterone, pattern hair loss became more common within a year. We found no trial in men on TRT that measured hair as an outcome.
So the useful question is less “will it happen” and more “would I notice if it did.” A baseline before the first dose and matched photos afterwards answer the second question far better than the mirror can.
TL;DR
- Pattern hair loss is linked to DHT and to inherited sensitivity of the hair follicle to it.
- The AndroGel 1.62% label lists alopecia among reactions reported after approval; those reports cannot show cause or frequency.
- In a one-year study of 53 trans men starting testosterone, pattern hair loss became more common.
- We found no trial in men treated for low testosterone that measured hair as an outcome.
- Take baseline photos before the first dose, keep a dated log, and bring any change to your prescriber.
Important
This article is educational and not medical advice. If you are worried about sudden shedding, scalp symptoms, or side effects, talk to a licensed clinician.
How testosterone connects to pattern hair loss
Male pattern hair loss is related to androgens, and in particular to dihydrotestosterone (DHT). The only gene confirmed to play a part is the androgen receptor gene: some variants make the receptor easier to stimulate, which is thought to make follicles more sensitive to DHT (MedlinePlus Genetics: androgenetic alopecia). The body makes DHT from testosterone with an enzyme called 5-alpha reductase; the DHT explainer covers that step.
That gives a reason to expect TRT could matter for hair in people who are already prone to pattern loss. It is a reason, not a measurement. How much extra hair loss TRT causes, and in whom, has not been studied directly in men treated for low testosterone.
What the labels say
The prescribing information for AndroGel 1.62%, a testosterone gel, lists alopecia under skin reactions identified after approval. The label explains that these reports came in voluntarily from a population of unknown size, so it is not always possible to estimate how often they happen or to show the drug caused them (AndroGel 1.62% label on DailyMed). The MedlinePlus guide to testosterone injection lists male-pattern hair loss among the effects testosterone may cause in women (MedlinePlus: testosterone injection).
The clearest evidence comes from trans men
A European study followed 53 trans men for one year after they started testosterone injections. Testosterone increased acne, facial and body hair, and the share of men with androgenetic alopecia, the medical name for pattern hair loss (Wierckx and colleagues, 2014). A 2026 randomised trial in trans people on testosterone opens with the same point: people receiving testosterone may develop androgenetic alopecia. The trial itself tested a treatment for hair loss that had already started in that group; it is not a guide for anyone else (Tang and colleagues, 2026).
These results may not transfer directly to TRT. Trans men move from female-typical to male-typical testosterone levels, while the Endocrine Society guideline for men with low testosterone suggests aiming for the middle of the normal range (Bhasin and colleagues, 2018). The size of the change is different, and so may be the effect on hair.
What is not known
- How often TRT starts or speeds up hair loss in men treated for low testosterone. A PubMed search on 2 November 2026 found no trial in this group with hair as an outcome.
- Whether family history predicts who loses hair on TRT. It is a reasonable guess from the genetics, but it has not been tested in TRT users.
- Whether gels, injections or other forms differ for hair.
- Whether hair lost during TRT returns if the therapy stops.
What to record before and after you start
Pattern hair loss moves slowly, and a change over a few weeks is easy to blame on lighting or a haircut. A record that starts before the first dose is what makes a later comparison fair.
- Baseline photos before the first dose: hairline, both temples and the crown from above, in fixed light, distance and angle, with hair dry and styled the same way.
- Matched photos later: the same set at regular points, compared months apart rather than weeks. See how often to take progress photos.
- Dates and changes: the start date, the form of testosterone, and any change your prescriber makes.
- Shedding notes: on wash days, describe the hair you see in the drain the same way each time, so a lasting rise stands out from one bad day.
- Context: family history of hair loss, and any other medicine, illness or big life change, as notes for your doctor rather than a diagnosis. The family history checklist helps you write it down.
Blood tests belong to your prescriber, not to a hair log. The Endocrine Society guideline describes monitoring men on testosterone with a standard plan that checks symptoms, side effects, testosterone and hematocrit levels, and prostate cancer risk in the first year (Bhasin and colleagues, 2018). A clear photo record of your hair is something you can add to those visits.
When to talk to your prescriber or a dermatologist
Bring it up if your matched photos show the hairline, temples or crown thinning across several months, or if shedding stays high. Questions about finasteride or other hair treatments while on testosterone belong with the clinician who manages your hormones, who knows your health and your goals. Do not stop or change your therapy on your own. See a doctor sooner for round patches, redness, scaling or scalp pain, which point away from pattern hair loss; a dermatologist diagnoses hair loss from your history and a scalp exam (AAD diagnosis overview).
Next step
Before your first dose, take one baseline set of hairline, temple and crown photos in fixed light, and write down the date. Repeat the same set at regular points and compare months, not weeks. If the trend slides, you will have a record to show your prescriber.
Related reading
Sources: Wierckx et al. 2014, Journal of Sexual Medicine; Tang et al. 2026, Journal of the American Academy of Dermatology; Bhasin et al. 2018, Endocrine Society guideline, J Clin Endocrinol Metab; AndroGel 1.62% (testosterone gel) prescribing information, DailyMed; MedlinePlus: testosterone injection; MedlinePlus Genetics: androgenetic alopecia; AAD: hair loss diagnosis and treatment.
